From patchwork Mon Jul 1 13:57:55 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 13718176 X-Patchwork-Delegate: herbert@gondor.apana.org.au Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 26D4415EFB0; Mon, 1 Jul 2024 13:58:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842301; cv=none; b=eN73GNa05TTjUdvxSXuH7Js6jQVo0j2/FCHhU6kk+ui+pbtdSS+t8eA5Eq0DCylTnOq0+V830scuGuraxBVFzuSyOD+IBqqiYT+/5iQuyTXSGHdQiv7KEVb7fOKFfW05N2GOYZHGppC5J1NuugoFbbV3HAL6hMwAY6Xlklni4eQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842301; c=relaxed/simple; bh=5jnp+kHd3g/+qHCFwDqIaPslwszjyFWsAceh3rFkPT4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EKalq1GDd39+YQLzx14fRYrmBmGXI/mX4zN13ggIrkqUX/Cxkuq4EPc7YAxTrNg3s48H64Jop9bSh4T4j/XTkVMMK8ftZ9bgXeWylEeyYzfjS460PEDXFVp6wfLowfKDbrCTgmZipAjTuwu/7SHo2Ua03lAWy7CThVZUpg2u2fI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b=ZC6gWGLF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="ZC6gWGLF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC0F9C4AF11; Mon, 1 Jul 2024 13:58:19 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="ZC6gWGLF" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1719842299; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=W1D7HNr+ZwtoxrFYBn1Uli4yI71rvOS/zftFZSDcwfM=; b=ZC6gWGLFx2DP0ik4g2DrtBMMGi1ZOIHotBAdSmlkdOQ/BvJ/pnfprxm3eRMue0+EIpDuMs Cpssw+UGuAauybC7BHqH3tEm2uvEPOVinGjJSkrmYsG6BSHXmaydV6p6EBsDDQR2dnAb8q o6sgkWVEpl6NLtfdCMvws10Ylq05Bok= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 77d760b3 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 1 Jul 2024 13:58:19 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de Cc: "Jason A. Donenfeld" , linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand , linux-mm@kvack.org Subject: [PATCH v19 1/5] mm: add VM_DROPPABLE for designating always lazily freeable mappings Date: Mon, 1 Jul 2024 15:57:55 +0200 Message-ID: <20240701135801.3698-2-Jason@zx2c4.com> In-Reply-To: <20240701135801.3698-1-Jason@zx2c4.com> References: <20240701135801.3698-1-Jason@zx2c4.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The vDSO getrandom() implementation works with a buffer allocated with a new system call that has certain requirements: - It shouldn't be written to core dumps. * Easy: VM_DONTDUMP. - It should be zeroed on fork. * Easy: VM_WIPEONFORK. - It shouldn't be written to swap. * Uh-oh: mlock is rlimited. * Uh-oh: mlock isn't inherited by forks. It turns out that the vDSO getrandom() function has three really nice characteristics that we can exploit to solve this problem: 1) Due to being wiped during fork(), the vDSO code is already robust to having the contents of the pages it reads zeroed out midway through the function's execution. 2) In the absolute worst case of whatever contingency we're coding for, we have the option to fallback to the getrandom() syscall, and everything is fine. 3) The buffers the function uses are only ever useful for a maximum of 60 seconds -- a sort of cache, rather than a long term allocation. These characteristics mean that we can introduce VM_DROPPABLE, which has the following semantics: a) It never is written out to swap. b) Under memory pressure, mm can just drop the pages (so that they're zero when read back again). c) It is inherited by fork. d) It doesn't count against the mlock budget, since nothing is locked. This is fairly simple to implement, with the one snag that we have to use 64-bit VM_* flags, but this shouldn't be a problem, since the only consumers will probably be 64-bit anyway. This way, allocations used by vDSO getrandom() can use: VM_DROPPABLE | VM_DONTDUMP | VM_WIPEONFORK | VM_NORESERVE And there will be no problem with using memory when not in use, not wiping on fork(), coredumps, or writing out to swap. Cc: linux-mm@kvack.org Signed-off-by: Jason A. Donenfeld --- fs/proc/task_mmu.c | 3 +++ include/linux/mm.h | 8 ++++++++ include/trace/events/mmflags.h | 7 +++++++ mm/Kconfig | 3 +++ mm/mprotect.c | 2 +- mm/rmap.c | 8 +++++--- 6 files changed, 27 insertions(+), 4 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 71e5039d940d..b3bd8432f869 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -709,6 +709,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma) #endif #ifdef CONFIG_64BIT [ilog2(VM_SEALED)] = "sl", +#endif +#ifdef CONFIG_NEED_VM_DROPPABLE + [ilog2(VM_DROPPABLE)] = "dp", #endif }; size_t i; diff --git a/include/linux/mm.h b/include/linux/mm.h index eb7c96d24ac0..92454a0272ce 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -321,12 +321,14 @@ extern unsigned int kobjsize(const void *objp); #define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */ #define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectures */ #define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectures */ +#define VM_HIGH_ARCH_BIT_6 38 /* bit only usable on 64-bit architectures */ #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0) #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1) #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2) #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3) #define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4) #define VM_HIGH_ARCH_5 BIT(VM_HIGH_ARCH_BIT_5) +#define VM_HIGH_ARCH_6 BIT(VM_HIGH_ARCH_BIT_6) #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */ #ifdef CONFIG_ARCH_HAS_PKEYS @@ -357,6 +359,12 @@ extern unsigned int kobjsize(const void *objp); # define VM_SHADOW_STACK VM_NONE #endif +#ifdef CONFIG_NEED_VM_DROPPABLE +# define VM_DROPPABLE VM_HIGH_ARCH_6 +#else +# define VM_DROPPABLE VM_NONE +#endif + #if defined(CONFIG_X86) # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ #elif defined(CONFIG_PPC) diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h index e46d6e82765e..fab7848df50a 100644 --- a/include/trace/events/mmflags.h +++ b/include/trace/events/mmflags.h @@ -165,6 +165,12 @@ IF_HAVE_PG_ARCH_X(arch_3) # define IF_HAVE_UFFD_MINOR(flag, name) #endif +#ifdef CONFIG_NEED_VM_DROPPABLE +# define IF_HAVE_VM_DROPPABLE(flag, name) {flag, name}, +#else +# define IF_HAVE_VM_DROPPABLE(flag, name) +#endif + #define __def_vmaflag_names \ {VM_READ, "read" }, \ {VM_WRITE, "write" }, \ @@ -197,6 +203,7 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \ {VM_MIXEDMAP, "mixedmap" }, \ {VM_HUGEPAGE, "hugepage" }, \ {VM_NOHUGEPAGE, "nohugepage" }, \ +IF_HAVE_VM_DROPPABLE(VM_DROPPABLE, "droppable" ) \ {VM_MERGEABLE, "mergeable" } \ #define show_vma_flags(flags) \ diff --git a/mm/Kconfig b/mm/Kconfig index b4cb45255a54..6cd65ea4b3ad 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1056,6 +1056,9 @@ config ARCH_USES_HIGH_VMA_FLAGS bool config ARCH_HAS_PKEYS bool +config NEED_VM_DROPPABLE + select ARCH_USES_HIGH_VMA_FLAGS + bool config ARCH_USES_PG_ARCH_X bool diff --git a/mm/mprotect.c b/mm/mprotect.c index 8c6cd8825273..57b8dad9adcc 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -623,7 +623,7 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb, may_expand_vm(mm, oldflags, nrpages)) return -ENOMEM; if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB| - VM_SHARED|VM_NORESERVE))) { + VM_SHARED|VM_NORESERVE|VM_DROPPABLE))) { charged = nrpages; if (security_vm_enough_memory_mm(mm, charged)) return -ENOMEM; diff --git a/mm/rmap.c b/mm/rmap.c index e8fc5ecb59b2..d873a3f06506 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1397,7 +1397,8 @@ void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio); VM_BUG_ON_VMA(address < vma->vm_start || address + (nr << PAGE_SHIFT) > vma->vm_end, vma); - __folio_set_swapbacked(folio); + if (!(vma->vm_flags & VM_DROPPABLE)) + __folio_set_swapbacked(folio); __folio_set_anon(folio, vma, address, true); if (likely(!folio_test_large(folio))) { @@ -1841,7 +1842,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * plus the rmap(s) (dropped by discard:). */ if (ref_count == 1 + map_count && - !folio_test_dirty(folio)) { + (!folio_test_dirty(folio) || (vma->vm_flags & VM_DROPPABLE))) { dec_mm_counter(mm, MM_ANONPAGES); goto discard; } @@ -1851,7 +1852,8 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, * discarded. Remap the page to page table. */ set_pte_at(mm, address, pvmw.pte, pteval); - folio_set_swapbacked(folio); + if (!(vma->vm_flags & VM_DROPPABLE)) + folio_set_swapbacked(folio); ret = false; page_vma_mapped_walk_done(&pvmw); break; From patchwork Mon Jul 1 13:57:56 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 13718177 X-Patchwork-Delegate: herbert@gondor.apana.org.au Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D20FF15EFB6; Mon, 1 Jul 2024 13:58:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842305; cv=none; b=ozCad5zanZCsDP9HFEBun3rv42/DRIAlCK8nYZEk/HaYlb1QzJl9dJ2Sl3banNQC9LTiOA+7IRydJDHyypZFPWGQxvBsSB1XgSqyGORfxIMeUBULM2vBp8uDbvEr2umHheMBtwiTF2i/K4zvHIO1Lxo7aPx9/2i033k1ox257PY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842305; c=relaxed/simple; bh=TPfuYSXl+p5QBRw+BQI54J9G8AeQZl0U/hLxHaSW6RQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PqWF9wcHlR4jg+yFRjxiCjlLNo1aCX5UoXQA+YX3A/+3aJNIM/RqVERSSUdBjTQkB61KWnXyVz2KoeyAlslYch4pTmZgVrqu0cbMTbvKyhlp+JEeL5bzr18GGLH1dGwjlTSX4B53dgIcEmEgFaxjyCnehIeMZolg5p3QjFCs+14= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b=PXp71Ugp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="PXp71Ugp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3EB2EC4AF0D; Mon, 1 Jul 2024 13:58:23 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="PXp71Ugp" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1719842302; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BtBkefDwCG5Ua2IrBC22KFVu5x+6eB/qzPWKFjFCZrQ=; b=PXp71UgpZuWBaejt41e6x/Orvx0hsqfagr/SempA+8aUEak+aa8MG/CEErXnh9fp1hP9qD YCM4XnR2vD2ifmYpbIg1aVYmS1h3KMzjaioPPI7yhacmJgEoAgUw1Lg+6ldlbQeJShgqKd +V7dAVoGDms86M5C5GiUsU1m7jgT210= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 583cb2b7 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 1 Jul 2024 13:58:22 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de Cc: "Jason A. Donenfeld" , linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand Subject: [PATCH v19 2/5] random: add vgetrandom_alloc() syscall Date: Mon, 1 Jul 2024 15:57:56 +0200 Message-ID: <20240701135801.3698-3-Jason@zx2c4.com> In-Reply-To: <20240701135801.3698-1-Jason@zx2c4.com> References: <20240701135801.3698-1-Jason@zx2c4.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The vDSO getrandom() works over an opaque per-thread state of an unexported size, which must be marked VM_WIPEONFORK, VM_DONTDUMP, VM_NORESERVE, and VM_DROPPABLE for proper operation. Over time, the nuances of these allocations may change or grow or even differ based on architectural features. The syscall uses the extensible struct pattern: struct vgetrandom_alloc_args { u64 flags; u64 num; u64 size_per_each; u64 bytes_allocated; }; void *vgetrandom_alloc(struct vgetrandom_alloc_args *args, size_t args_len); This takes a hinted number of opaque states in @num, and returns a pointer to an array of opaque states, the number of states actually allocated back in @num, the size in bytes of each one in @size_per_each, and the size of the total allocation in @bytes_allocated, enabling a libc to slice up the returned array into a state per each thread, while ensuring that no single state straddles a page boundary. (The @flags argument, as well as the @size_per_each and @bytes_allocated input values, are reserved for the future and are forced to be zero for now.) Libc is expected to allocate a chunk of these on first use, and then dole them out to threads as they're created, allocating more when needed. The returned address of the first state may be passed to munmap(2) with a length @bytes_allocated in order to deallocate the memory. We very intentionally do *not* leave state allocation for vDSO getrandom() up to userspace itself, but rather provide this new syscall for such allocations. vDSO getrandom() must not store its state in just any old memory address, but rather just ones that the kernel specially allocates for it, leaving the particularities of those allocations up to the kernel. The allocation of states is intended to be integrated into libc's thread management. As an illustrative example, the following code might be used to do the same outside of libc. Though, vgetrandom_alloc() is not expected to be exposed outside of libc, and the pthread usage here is expected to be elided into libc internals. This allocation scheme is very naive and does not shrink; other implementations may choose to be more complex. static void *vgetrandom_alloc(size_t *num, size_t *size_per_each, size_t *bytes_allocated) { enum { __NR_vgetrandom_alloc = 463 }; struct vgetrandom_alloc_args args = { .num = *num }; void *ret = (void *)syscall(__NR_vgetrandom_alloc, &args, VGETRANDOM_ALLOC_ARGS_SIZE_VER0); if (ret != MAP_FAILED) { *num = args.num; *size_per_each = args.size_per_each; *bytes_allocated = args.bytes_allocated; } return ret; } static struct { pthread_mutex_t lock; void **states; size_t len, cap, size_per_each; } grnd_allocator = { .lock = PTHREAD_MUTEX_INITIALIZER }; static void *vgetrandom_get_state(void) { void *state = NULL; pthread_mutex_lock(&grnd_allocator.lock); if (!grnd_allocator.len) { size_t page_size = getpagesize(); size_t new_cap; size_t bytes_allocated, size_per_each, num = sysconf(_SC_NPROCESSORS_ONLN); /* Just a decent heuristic. */ void *new_block = vgetrandom_alloc(&num, &size_per_each, &bytes_allocated); void *new_states; if (new_block == MAP_FAILED) goto out; if (grnd_allocator.size_per_each && grnd_allocator.size_per_each != size_per_each) goto unmap; grnd_allocator.size_per_each = size_per_each; new_cap = grnd_allocator.cap + num; new_states = reallocarray(grnd_allocator.states, new_cap, sizeof(*grnd_allocator.states)); if (!new_states) goto unmap; grnd_allocator.cap = new_cap; grnd_allocator.states = new_states; for (size_t i = 0; i < num; ++i) { grnd_allocator.states[i] = new_block; if (((uintptr_t)new_block & (page_size - 1)) + size_per_each > page_size) new_block = (void *)(((uintptr_t)new_block + page_size) & (page_size - 1)); else new_block += size_per_each; } grnd_allocator.len = num; goto success; unmap: munmap(new_block, bytes_allocated); goto out; } success: state = grnd_allocator.states[--grnd_allocator.len]; out: pthread_mutex_unlock(&grnd_allocator.lock); return state; } static void vgetrandom_put_state(void *state) { if (!state) return; pthread_mutex_lock(&grnd_allocator.lock); grnd_allocator.states[grnd_allocator.len++] = state; pthread_mutex_unlock(&grnd_allocator.lock); } Signed-off-by: Jason A. Donenfeld --- MAINTAINERS | 1 + drivers/char/random.c | 127 +++++++++++++++++++++++++++++++++++- include/linux/syscalls.h | 3 + include/uapi/linux/random.h | 17 +++++ include/vdso/getrandom.h | 16 +++++ kernel/sys_ni.c | 3 + lib/vdso/Kconfig | 6 ++ 7 files changed, 172 insertions(+), 1 deletion(-) create mode 100644 include/vdso/getrandom.h diff --git a/MAINTAINERS b/MAINTAINERS index 3c4fdf74a3f9..2fbd8f11093c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18747,6 +18747,7 @@ T: git https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git F: Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml F: drivers/char/random.c F: drivers/virt/vmgenid.c +F: include/vdso/getrandom.h RAPIDIO SUBSYSTEM M: Matt Porter diff --git a/drivers/char/random.c b/drivers/char/random.c index 2597cb43f438..be95affc0638 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1,6 +1,6 @@ // SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) /* - * Copyright (C) 2017-2022 Jason A. Donenfeld . All Rights Reserved. + * Copyright (C) 2017-2024 Jason A. Donenfeld . All Rights Reserved. * Copyright Matt Mackall , 2003, 2004, 2005 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All rights reserved. * @@ -8,6 +8,7 @@ * into roughly six sections, each with a section header: * * - Initialization and readiness waiting. + * - vDSO support helpers. * - Fast key erasure RNG, the "crng". * - Entropy accumulation and extraction routines. * - Entropy collection routines. @@ -39,6 +40,7 @@ #include #include #include +#include #include #include #include @@ -56,6 +58,9 @@ #include #include #include +#ifdef CONFIG_VDSO_GETRANDOM +#include +#endif #include #include #include @@ -169,6 +174,126 @@ int __cold execute_with_initialized_rng(struct notifier_block *nb) __func__, (void *)_RET_IP_, crng_init) + +/******************************************************************** + * + * vDSO support helpers. + * + * The actual vDSO function is defined over in lib/vdso/getrandom.c, + * but this section contains the kernel-mode helpers to support that. + * + ********************************************************************/ + +#ifdef CONFIG_VDSO_GETRANDOM +/** + * sys_vgetrandom_alloc - Allocate opaque states for use with vDSO getrandom(). + * + * This takes a struct vgetrandom_alloc_args argument and its size, versioning + * it, which contains these members: + * + * @flags: Reserved flags, must currently always be zero. + * + * @num: On input, a suggested hint of how many states to allocate. On + * return, the number of states actually allocated. + * + * @size_per_each: On input, must currently be zero. On return, the size of each + * state allocated, so that the caller can split up the returned + * allocation into individual states. + * + * @bytes_allocated: On input, must currently be zero. On return, the total number + * of bytes allocated, which may be passed to munmap(2) for + * deallocating. + * + * The getrandom() vDSO function in userspace requires an opaque state, which + * this function allocates by mapping a certain number of special pages into + * the calling process. It takes a hint as to the number of opaque states + * desired, and provides the caller with the number of opaque states actually + * allocated, the size of each one in bytes, and the address of the first + * state, which may be split up into @num states of @size_per_each bytes each, + * by adding @size_per_each to the returned first state @num times, while + * ensuring that no single state straddles a page boundary. + * + * Returns the address of the first state in the allocation on success, or a + * negative error value on failure. + * + * The returned address of the first state may be passed to munmap(2) with a + * length of @bytes_allocated, in order to deallocate the memory, after which + * it is invalid to pass it to vDSO getrandom(). + * + * States allocated by this function must not be dereferenced, written, read, + * or otherwise manipulated. The *only* supported operations are: + * - Splitting up the states in intervals of @size_per_each, no more than + * @num times from the first state, while ensuring that no single state + * straddles a page boundary. + * - Passing a state to the getrandom() vDSO function's @opaque_state + * parameter, but not passing the same state at the same time to two such + * calls. + * - Passing the first state and the total length to munmap(2), as described + * above. + * All other uses are undefined behavior, which is subject to change or removal. + */ +SYSCALL_DEFINE2(vgetrandom_alloc, struct vgetrandom_alloc_args __user *, uargs, + size_t, uargs_size) +{ + size_t state_size, alloc_size, num_states; + unsigned long pages_addr, populate; + struct vgetrandom_alloc_args args; + vm_flags_t vm_flags; + + /* Currently only one published version of the struct. */ + if (uargs_size != sizeof(args)) + return -EINVAL; + if (copy_from_user(&args, uargs, sizeof(args))) + return -EFAULT; + /* These are currently reserved to be zero on input. */ + if (args.flags || args.size_per_each || args.bytes_allocated) + return -EINVAL; + + state_size = sizeof(struct vgetrandom_state); + num_states = clamp_t(size_t, args.num, 1, (SIZE_MAX & PAGE_MASK) / state_size); + alloc_size = PAGE_ALIGN(num_states * state_size); + /* + * States cannot straddle page boundaries, so calculate the number of + * states that can fit inside of a page without being split, and then + * multiply that out by the number of pages allocated. + */ + num_states = (PAGE_SIZE / state_size) * (alloc_size / PAGE_SIZE); + + vm_flags = + /* + * Don't allow state to be written to swap, to preserve forward secrecy. + * But also don't mlock it or pre-reserve it, and allow it to + * be discarded under memory pressure. If no memory is available, returns + * zeros rather than segfaulting. + */ + VM_DROPPABLE | VM_NORESERVE | + + /* Don't allow the state to survive forks, to prevent random number re-use. */ + VM_WIPEONFORK | + + /* Don't write random state into coredumps. */ + VM_DONTDUMP; + + if (mmap_write_lock_killable(current->mm)) + return -EINTR; + pages_addr = do_mmap(NULL, 0, alloc_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, vm_flags, 0, &populate, NULL); + mmap_write_unlock(current->mm); + if (IS_ERR_VALUE(pages_addr)) + return pages_addr; + + args.num = num_states; + args.size_per_each = state_size; + args.bytes_allocated = alloc_size; + if (copy_to_user(uargs, &args, sizeof(args))) { + vm_munmap(pages_addr, alloc_size); + return -EFAULT; + } + + return pages_addr; +} +#endif + /********************************************************************* * * Fast key erasure RNG, the "crng". diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 63424af87bba..14e47fec5089 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -906,6 +906,9 @@ asmlinkage long sys_seccomp(unsigned int op, unsigned int flags, void __user *uargs); asmlinkage long sys_getrandom(char __user *buf, size_t count, unsigned int flags); +asmlinkage long sys_vgetrandom_alloc(unsigned int __user *num, + unsigned int __user *size_per_each, + unsigned long addr, unsigned int flags); asmlinkage long sys_memfd_create(const char __user *uname_ptr, unsigned int flags); asmlinkage long sys_bpf(int cmd, union bpf_attr __user *attr, unsigned int size); asmlinkage long sys_execveat(int dfd, const char __user *filename, diff --git a/include/uapi/linux/random.h b/include/uapi/linux/random.h index e744c23582eb..c61b02335e19 100644 --- a/include/uapi/linux/random.h +++ b/include/uapi/linux/random.h @@ -55,4 +55,21 @@ struct rand_pool_info { #define GRND_RANDOM 0x0002 #define GRND_INSECURE 0x0004 +/** + * struct vgetrandom_alloc_args - arguments for the vgetrandom_alloc syscall + * + * The arguments are described in the doc comment of vgetrandom_alloc. + * + * The structure is versioned by size and thus extensible. New struct members + * must go at the end of the struct and must be properly 64-bit aligned. + */ +struct vgetrandom_alloc_args { + __aligned_u64 flags; + __aligned_u64 num; + __aligned_u64 size_per_each; + __aligned_u64 bytes_allocated; +}; + +#define VGETRANDOM_ALLOC_ARGS_SIZE_VER0 32 /* sizeof first published struct */ + #endif /* _UAPI_LINUX_RANDOM_H */ diff --git a/include/vdso/getrandom.h b/include/vdso/getrandom.h new file mode 100644 index 000000000000..69037519d20b --- /dev/null +++ b/include/vdso/getrandom.h @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2022-2024 Jason A. Donenfeld . All Rights Reserved. + */ + +#ifndef _VDSO_GETRANDOM_H +#define _VDSO_GETRANDOM_H + +/** + * struct vgetrandom_state - State used by vDSO getrandom() and allocated by vgetrandom_alloc(). + * + * Currently empty, as the vDSO getrandom() function has not yet been implemented. + */ +struct vgetrandom_state { int placeholder; }; + +#endif /* _VDSO_GETRANDOM_H */ diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index b696b85ac63e..4e3728a8a8f4 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -272,6 +272,9 @@ COND_SYSCALL(pkey_free); /* memfd_secret */ COND_SYSCALL(memfd_secret); +/* random */ +COND_SYSCALL(vgetrandom_alloc); + /* * Architecture specific weak syscall entries. */ diff --git a/lib/vdso/Kconfig b/lib/vdso/Kconfig index c46c2300517c..99661b731834 100644 --- a/lib/vdso/Kconfig +++ b/lib/vdso/Kconfig @@ -38,3 +38,9 @@ config GENERIC_VDSO_OVERFLOW_PROTECT in the hotpath. endif + +config VDSO_GETRANDOM + bool + select NEED_VM_DROPPABLE + help + Selected by architectures that support vDSO getrandom(). From patchwork Mon Jul 1 13:57:57 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 13718178 X-Patchwork-Delegate: herbert@gondor.apana.org.au Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E7C7160787; Mon, 1 Jul 2024 13:58:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842308; cv=none; b=gI+QC12DhsZZTL/WkKrOWLIzam3dRpGblE9XRbchBP93cQJKw15VggWpRpxJXGX6fEqoGliWxKp74T0fkbKS9Vq+g3JI8UNFB8zTkI5wza6jEooAJdGb74cl4WHDnicLLdIZMQT5/6zyWaplbiYo3kPAKecXupuWbkl28Ddfu4g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842308; c=relaxed/simple; bh=Ro9YX2Zjp+63xUypUEmdy/xzEBKeP3Bz67rn9HJOpsU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=N0YAqhmpO1SZPzjgDjwbvRCExUA0KY+Qna24owzbXYvBFsgXtQhhwpHLCaQeIGy8knaon/qKhi/rbbDR95xH2f6nwFCDUCE+9/xANDF2T4YhmwUcz+0tZUUE1rLHrDcPoiVpX2TOIbAaCBe6ki2fWAYGJgWaQfZEc1Yved2JqGc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b=lOImEcbO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="lOImEcbO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6867C116B1; Mon, 1 Jul 2024 13:58:26 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="lOImEcbO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1719842306; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Z3CrsyJkavXDJB+79Q1Sa86e6Oqov9BpqdS9+jDu+08=; b=lOImEcbO/3wmf/GnXuY7mzA7/l4JiaThaPzE9xdjvWgsQV9MW1QMfjabKvcKbMRSyCD4+R loyVdLCp/OFZytO60mA36x3SGmStsVOFLnKe62Ph6rvGRD2AnDrWsIe1mdM1IXGxESZBG5 hKk+zm2Krv+X1EEFIBZa7qTF56Jqack= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id a3d044e7 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 1 Jul 2024 13:58:25 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de Cc: "Jason A. Donenfeld" , linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand , Geert Uytterhoeven Subject: [PATCH v19 3/5] arch: allocate vgetrandom_alloc() syscall number Date: Mon, 1 Jul 2024 15:57:57 +0200 Message-ID: <20240701135801.3698-4-Jason@zx2c4.com> In-Reply-To: <20240701135801.3698-1-Jason@zx2c4.com> References: <20240701135801.3698-1-Jason@zx2c4.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add vgetrandom_alloc() as syscall 463 (or 573 on alpha) by adding it to all of the various syscall.tbl and unistd.h files. Acked-by: Geert Uytterhoeven Signed-off-by: Jason A. Donenfeld --- arch/alpha/kernel/syscalls/syscall.tbl | 1 + arch/arm/tools/syscall.tbl | 1 + arch/arm64/include/asm/unistd32.h | 2 ++ arch/m68k/kernel/syscalls/syscall.tbl | 1 + arch/microblaze/kernel/syscalls/syscall.tbl | 1 + arch/mips/kernel/syscalls/syscall_n32.tbl | 1 + arch/mips/kernel/syscalls/syscall_n64.tbl | 1 + arch/mips/kernel/syscalls/syscall_o32.tbl | 1 + arch/parisc/kernel/syscalls/syscall.tbl | 1 + arch/powerpc/kernel/syscalls/syscall.tbl | 1 + arch/s390/kernel/syscalls/syscall.tbl | 1 + arch/sh/kernel/syscalls/syscall.tbl | 1 + arch/sparc/kernel/syscalls/syscall.tbl | 1 + arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + arch/xtensa/kernel/syscalls/syscall.tbl | 1 + include/uapi/asm-generic/unistd.h | 5 ++++- tools/include/uapi/asm-generic/unistd.h | 5 ++++- tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl | 1 + tools/perf/arch/powerpc/entry/syscalls/syscall.tbl | 1 + tools/perf/arch/s390/entry/syscalls/syscall.tbl | 1 + tools/perf/arch/x86/entry/syscalls/syscall_64.tbl | 1 + 22 files changed, 29 insertions(+), 2 deletions(-) diff --git a/arch/alpha/kernel/syscalls/syscall.tbl b/arch/alpha/kernel/syscalls/syscall.tbl index 74720667fe09..8c38193bf86a 100644 --- a/arch/alpha/kernel/syscalls/syscall.tbl +++ b/arch/alpha/kernel/syscalls/syscall.tbl @@ -502,3 +502,4 @@ 570 common lsm_set_self_attr sys_lsm_set_self_attr 571 common lsm_list_modules sys_lsm_list_modules 572 common mseal sys_mseal +573 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl index 2ed7d229c8f9..118e41178905 100644 --- a/arch/arm/tools/syscall.tbl +++ b/arch/arm/tools/syscall.tbl @@ -476,3 +476,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h index 1386e8e751f2..f7a45c1788b3 100644 --- a/arch/arm64/include/asm/unistd32.h +++ b/arch/arm64/include/asm/unistd32.h @@ -931,6 +931,8 @@ __SYSCALL(__NR_lsm_set_self_attr, sys_lsm_set_self_attr) __SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules) #define __NR_mseal 462 __SYSCALL(__NR_mseal, sys_mseal) +#define __NR_vgetrandom_alloc 463 +__SYSCALL(__NR_vgetrandom_alloc, sys_vgetrandom_alloc) /* * Please add new compat syscalls above this comment and update diff --git a/arch/m68k/kernel/syscalls/syscall.tbl b/arch/m68k/kernel/syscalls/syscall.tbl index 22a3cbd4c602..bd919d1a8231 100644 --- a/arch/m68k/kernel/syscalls/syscall.tbl +++ b/arch/m68k/kernel/syscalls/syscall.tbl @@ -462,3 +462,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/microblaze/kernel/syscalls/syscall.tbl b/arch/microblaze/kernel/syscalls/syscall.tbl index 2b81a6bd78b2..d3d3c017a5bb 100644 --- a/arch/microblaze/kernel/syscalls/syscall.tbl +++ b/arch/microblaze/kernel/syscalls/syscall.tbl @@ -468,3 +468,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl index 953f5b7dc723..502cedc0f84d 100644 --- a/arch/mips/kernel/syscalls/syscall_n32.tbl +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl @@ -401,3 +401,4 @@ 460 n32 lsm_set_self_attr sys_lsm_set_self_attr 461 n32 lsm_list_modules sys_lsm_list_modules 462 n32 mseal sys_mseal +463 n32 vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl index 1464c6be6eb3..33710f855c46 100644 --- a/arch/mips/kernel/syscalls/syscall_n64.tbl +++ b/arch/mips/kernel/syscalls/syscall_n64.tbl @@ -377,3 +377,4 @@ 460 n64 lsm_set_self_attr sys_lsm_set_self_attr 461 n64 lsm_list_modules sys_lsm_list_modules 462 n64 mseal sys_mseal +463 n64 vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl index 2439a2491cff..f342d3f26396 100644 --- a/arch/mips/kernel/syscalls/syscall_o32.tbl +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl @@ -450,3 +450,4 @@ 460 o32 lsm_set_self_attr sys_lsm_set_self_attr 461 o32 lsm_list_modules sys_lsm_list_modules 462 o32 mseal sys_mseal +463 o32 vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl index 66dc406b12e4..cddae8bc6fd5 100644 --- a/arch/parisc/kernel/syscalls/syscall.tbl +++ b/arch/parisc/kernel/syscalls/syscall.tbl @@ -461,3 +461,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl index ebae8415dfbb..5c01ec49f510 100644 --- a/arch/powerpc/kernel/syscalls/syscall.tbl +++ b/arch/powerpc/kernel/syscalls/syscall.tbl @@ -553,3 +553,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl index 01071182763e..f5abf7e496ee 100644 --- a/arch/s390/kernel/syscalls/syscall.tbl +++ b/arch/s390/kernel/syscalls/syscall.tbl @@ -465,3 +465,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl index c55fd7696d40..b911231478ee 100644 --- a/arch/sh/kernel/syscalls/syscall.tbl +++ b/arch/sh/kernel/syscalls/syscall.tbl @@ -466,3 +466,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl index cfdfb3707c16..7578d0dee5b1 100644 --- a/arch/sparc/kernel/syscalls/syscall.tbl +++ b/arch/sparc/kernel/syscalls/syscall.tbl @@ -508,3 +508,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index d6ebcab1d8b2..c4fc7c4f65c3 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -467,3 +467,4 @@ 460 i386 lsm_set_self_attr sys_lsm_set_self_attr 461 i386 lsm_list_modules sys_lsm_list_modules 462 i386 mseal sys_mseal +463 i386 vgetrandom_alloc sys_vgetrandom_alloc diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index a396f6e6ab5b..441443ba2ae6 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -384,6 +384,7 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc # # Due to a historical design error, certain syscalls are numbered differently diff --git a/arch/xtensa/kernel/syscalls/syscall.tbl b/arch/xtensa/kernel/syscalls/syscall.tbl index 67083fc1b2f5..b9f64edd0b18 100644 --- a/arch/xtensa/kernel/syscalls/syscall.tbl +++ b/arch/xtensa/kernel/syscalls/syscall.tbl @@ -433,3 +433,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h index d4cc26932ff4..57371c90dc13 100644 --- a/include/uapi/asm-generic/unistd.h +++ b/include/uapi/asm-generic/unistd.h @@ -845,8 +845,11 @@ __SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules) #define __NR_mseal 462 __SYSCALL(__NR_mseal, sys_mseal) +#define __NR_vgetrandom_alloc 463 +__SYSCALL(__NR_vgetrandom_alloc, sys_vgetrandom_alloc) + #undef __NR_syscalls -#define __NR_syscalls 463 +#define __NR_syscalls 464 /* * 32 bit systems traditionally used different diff --git a/tools/include/uapi/asm-generic/unistd.h b/tools/include/uapi/asm-generic/unistd.h index d983c48a3b6a..e94210483f60 100644 --- a/tools/include/uapi/asm-generic/unistd.h +++ b/tools/include/uapi/asm-generic/unistd.h @@ -845,8 +845,11 @@ __SYSCALL(__NR_lsm_list_modules, sys_lsm_list_modules) #define __NR_mseal 462 __SYSCALL(__NR_mseal, sys_mseal) +#define __NR_vgetrandom_alloc 463 +__SYSCALL(__NR_vgetrandom_alloc, sys_vgetrandom_alloc) + #undef __NR_syscalls -#define __NR_syscalls 463 +#define __NR_syscalls 464 /* * 32 bit systems traditionally used different diff --git a/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl b/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl index 1464c6be6eb3..33710f855c46 100644 --- a/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl +++ b/tools/perf/arch/mips/entry/syscalls/syscall_n64.tbl @@ -377,3 +377,4 @@ 460 n64 lsm_set_self_attr sys_lsm_set_self_attr 461 n64 lsm_list_modules sys_lsm_list_modules 462 n64 mseal sys_mseal +463 n64 vgetrandom_alloc sys_vgetrandom_alloc diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl index 3656f1ca7a21..b1c3ae68014c 100644 --- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl +++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl @@ -549,3 +549,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc diff --git a/tools/perf/arch/s390/entry/syscalls/syscall.tbl b/tools/perf/arch/s390/entry/syscalls/syscall.tbl index bd0fee24ad10..1188429316c1 100644 --- a/tools/perf/arch/s390/entry/syscalls/syscall.tbl +++ b/tools/perf/arch/s390/entry/syscalls/syscall.tbl @@ -465,3 +465,4 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc sys_vgetrandom_alloc diff --git a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl index a396f6e6ab5b..441443ba2ae6 100644 --- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl +++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl @@ -384,6 +384,7 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common vgetrandom_alloc sys_vgetrandom_alloc # # Due to a historical design error, certain syscalls are numbered differently From patchwork Mon Jul 1 13:57:58 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 13718179 X-Patchwork-Delegate: herbert@gondor.apana.org.au Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BFE37160883; Mon, 1 Jul 2024 13:58:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842312; cv=none; b=pBJT6eGMoONaSYA5ItzN0D2ZdhFTZSwB8sp9LbIpQmD/gXNYxQcWKYIJ00oBdadTOPLSsAQeZftVjxyoKCNG2yRCQ6yiahfHjJwWxBxl0r68i8nyh2Q+3nhl/4KgFAXuUXD8ktRrNXIbmayV8YiWydoLGsVtjoS6sc71C/wZsnw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842312; c=relaxed/simple; bh=bcZoN60V9aU1Dnodumisj38Lc04zUnifLOoFQzzNh4g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dD7xmsmA3u+BxjYm2vWIbO2mhGlkdQeyzWf+zRInamjeXXj3yZheAvhPm8tNpbNH6/zLO14mVRBBFd/FOrNdhkOjayy+HQHjrSoGkQA6QhFSMeXjE6r/eecoweSvkKPQaglNf+RM9TxTohtoXqGaI/7qCuzPC0n37sYVZWXPlXg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b=X9L1xSy9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="X9L1xSy9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29DFEC32786; Mon, 1 Jul 2024 13:58:30 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="X9L1xSy9" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1719842309; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IneK/3gWJB0eh5yjjK9IEanfaeM4fc5NF9ftHyeKhMU=; b=X9L1xSy95cboSocvXwS9akm8c0Ws9/aZ8vSy6duJhyrxtxUsToymdyEIuVuVyEwUiFwkQb +9F03ioQeOzfBaMzO8GOvPxhJPA07MRTvV4q3FlgsJMuUEmR8ayoSj8BL3X80D4/BRFHs5 TBQDoBM5Jj8CWBbg9U+HtGpr5tv9Hls= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 0aebb22e (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 1 Jul 2024 13:58:29 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de Cc: "Jason A. Donenfeld" , linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand Subject: [PATCH v19 4/5] random: introduce generic vDSO getrandom() implementation Date: Mon, 1 Jul 2024 15:57:58 +0200 Message-ID: <20240701135801.3698-5-Jason@zx2c4.com> In-Reply-To: <20240701135801.3698-1-Jason@zx2c4.com> References: <20240701135801.3698-1-Jason@zx2c4.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Provide a generic C vDSO getrandom() implementation, which operates on an opaque state returned by vgetrandom_alloc() and produces random bytes the same way as getrandom(). This has the following API signature: ssize_t vgetrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len); The return value and the first three arguments are the same as ordinary getrandom(), while the last two arguments are a pointer to the opaque allocated state and its size. Were all five arguments passed to the getrandom() syscall, nothing different would happen, and the functions would have the exact same behavior. The actual vDSO RNG algorithm implemented is the same one implemented by drivers/char/random.c, using the same fast-erasure techniques as that. Should the in-kernel implementation change, so too will the vDSO one. It requires an implementation of ChaCha20 that does not use any stack, in order to maintain forward secrecy if a multi-threaded program forks (though this does not account for a similar issue with SA_SIGINFO copying registers to the stack), so this is left as an architecture-specific fill-in. Stack-less ChaCha20 is an easy algorithm to implement on a variety of architectures, so this shouldn't be too onerous. Initially, the state is keyless, and so the first call makes a getrandom() syscall to generate that key, and then uses it for subsequent calls. By keeping track of a generation counter, it knows when its key is invalidated and it should fetch a new one using the syscall. Later, more than just a generation counter might be used. Since MADV_WIPEONFORK is set on the opaque state, the key and related state is wiped during a fork(), so secrets don't roll over into new processes, and the same state doesn't accidentally generate the same random stream. The generation counter, as well, is always >0, so that the 0 counter is a useful indication of a fork() or otherwise uninitialized state. If the kernel RNG is not yet initialized, then the vDSO always calls the syscall, because that behavior cannot be emulated in userspace, but fortunately that state is short lived and only during early boot. If it has been initialized, then there is no need to inspect the `flags` argument, because the behavior does not change post-initialization regardless of the `flags` value. Since the opaque state passed to it is mutated, vDSO getrandom() is not reentrant, when used with the same opaque state, which libc should be mindful of. vgetrandom_alloc() and vDSO getrandom() provide the ability for userspace to generate random bytes quickly and safely, and are intended to be integrated into libc's thread management. As an illustrative example, together with the example code from "random: add vgetrandom_alloc() syscall", the following code might be used to do the same outside of libc. In a libc, only the non-static vgetrandom() function at the end would be exported as part of a getrandom() implementations, and the various pthread-isms are expected to be elided into libc internals. static struct { ssize_t(*fn)(void *, size_t, unsigned long, void *, size_t); pthread_key_t key; pthread_once_t initialized; } grnd_ctx = { .initialized = PTHREAD_ONCE_INIT }; static void vgetrandom_init(void) { if (pthread_key_create(&grnd_ctx.key, vgetrandom_put_state) != 0) return; grnd_ctx.fn = vdso_sym("LINUX_2.6", "__vdso_getrandom"); } ssize_t vgetrandom(void *buf, size_t len, unsigned long flags) { void *state; pthread_once(&grnd_ctx.initialized, vgetrandom_init); if (!grnd_ctx.fn) return getrandom(buf, len, flags); state = pthread_getspecific(grnd_ctx.key); if (!state) { state = vgetrandom_get_state(); if (pthread_setspecific(grnd_ctx.key, state) != 0) { vgetrandom_put_state(state); state = NULL; } if (!state) return getrandom(buf, len, flags); } return grnd_ctx.fn(buf, len, flags, state, grnd_allocator.size_per_each); } Reviewed-by: Thomas Gleixner Signed-off-by: Jason A. Donenfeld --- MAINTAINERS | 1 + drivers/char/random.c | 13 + include/vdso/datapage.h | 11 + include/vdso/getrandom.h | 34 +- lib/vdso/getrandom.c | 236 ++++++++++++++ tools/testing/selftests/vDSO/.gitignore | 1 + tools/testing/selftests/vDSO/Makefile | 4 + .../selftests/vDSO/vdso_test_getrandom.c | 296 ++++++++++++++++++ 8 files changed, 594 insertions(+), 2 deletions(-) create mode 100644 lib/vdso/getrandom.c create mode 100644 tools/testing/selftests/vDSO/vdso_test_getrandom.c diff --git a/MAINTAINERS b/MAINTAINERS index 2fbd8f11093c..798158329ad8 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18748,6 +18748,7 @@ F: Documentation/devicetree/bindings/rng/microsoft,vmgenid.yaml F: drivers/char/random.c F: drivers/virt/vmgenid.c F: include/vdso/getrandom.h +F: lib/vdso/getrandom.c RAPIDIO SUBSYSTEM M: Matt Porter diff --git a/drivers/char/random.c b/drivers/char/random.c index be95affc0638..bb5577f3339b 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -60,6 +60,7 @@ #include #ifdef CONFIG_VDSO_GETRANDOM #include +#include #endif #include #include @@ -396,6 +397,15 @@ static void crng_reseed(struct work_struct *work) if (next_gen == ULONG_MAX) ++next_gen; WRITE_ONCE(base_crng.generation, next_gen); +#ifdef CONFIG_VDSO_GETRANDOM + /* base_crng.generation's invalid value is ULONG_MAX, while + * _vdso_rng_data.generation's invalid value is 0, so add one to the + * former to arrive at the latter. Use smp_store_release so that this + * is ordered with the write above to base_crng.generation. Pairs with + * the smp_rmb() before the syscall in the vDSO code. + */ + smp_store_release(&_vdso_rng_data.generation, next_gen + 1); +#endif if (!static_branch_likely(&crng_is_ready)) crng_init = CRNG_READY; spin_unlock_irqrestore(&base_crng.lock, flags); @@ -846,6 +856,9 @@ static void __cold _credit_init_bits(size_t bits) if (static_key_initialized && system_unbound_wq) queue_work(system_unbound_wq, &set_ready); atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); +#ifdef CONFIG_VDSO_GETRANDOM + WRITE_ONCE(_vdso_rng_data.is_ready, true); +#endif wake_up_interruptible(&crng_init_wait); kill_fasync(&fasync, SIGIO, POLL_IN); pr_notice("crng init done\n"); diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h index d04d394db064..05e5787beb73 100644 --- a/include/vdso/datapage.h +++ b/include/vdso/datapage.h @@ -113,6 +113,16 @@ struct vdso_data { struct arch_vdso_data arch_data; }; +/** + * struct vdso_rng_data - vdso RNG state information + * @generation: counter representing the number of RNG reseeds + * @is_ready: boolean signaling whether the RNG is initialized + */ +struct vdso_rng_data { + u64 generation; + u8 is_ready; +}; + /* * We use the hidden visibility to prevent the compiler from generating a GOT * relocation. Not only is going through a GOT useless (the entry couldn't and @@ -124,6 +134,7 @@ struct vdso_data { */ extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden"))); extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden"))); +extern struct vdso_rng_data _vdso_rng_data __attribute__((visibility("hidden"))); /** * union vdso_data_store - Generic vDSO data page diff --git a/include/vdso/getrandom.h b/include/vdso/getrandom.h index 69037519d20b..84f523149d5d 100644 --- a/include/vdso/getrandom.h +++ b/include/vdso/getrandom.h @@ -6,11 +6,41 @@ #ifndef _VDSO_GETRANDOM_H #define _VDSO_GETRANDOM_H +#include + +#define CHACHA_KEY_SIZE 32 +#define CHACHA_BLOCK_SIZE 64 + /** * struct vgetrandom_state - State used by vDSO getrandom() and allocated by vgetrandom_alloc(). * - * Currently empty, as the vDSO getrandom() function has not yet been implemented. + * @batch: One and a half ChaCha20 blocks of buffered RNG output. + * + * @key: Key to be used for generating next batch. + * + * @batch_key: Union of the prior two members, which is exactly two full + * ChaCha20 blocks in size, so that @batch and @key can be filled + * together. + * + * @generation: Snapshot of @rng_info->generation in the vDSO data page at + * the time @key was generated. + * + * @pos: Offset into @batch of the next available random byte. + * + * @in_use: Reentrancy guard for reusing a state within the same thread + * due to signal handlers. */ -struct vgetrandom_state { int placeholder; }; +struct vgetrandom_state { + union { + struct { + u8 batch[CHACHA_BLOCK_SIZE * 3 / 2]; + u32 key[CHACHA_KEY_SIZE / sizeof(u32)]; + }; + u8 batch_key[CHACHA_BLOCK_SIZE * 2]; + }; + u64 generation; + u8 pos; + bool in_use; +}; #endif /* _VDSO_GETRANDOM_H */ diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c new file mode 100644 index 000000000000..5efcd0d0af6b --- /dev/null +++ b/lib/vdso/getrandom.c @@ -0,0 +1,236 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2022-2024 Jason A. Donenfeld . All Rights Reserved. + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +#define MEMCPY_AND_ZERO_SRC(type, dst, src, len) do { \ + while (len >= sizeof(type)) { \ + __put_unaligned_t(type, __get_unaligned_t(type, src), dst); \ + __put_unaligned_t(type, 0, src); \ + dst += sizeof(type); \ + src += sizeof(type); \ + len -= sizeof(type); \ + } \ +} while (0) + +static void memcpy_and_zero_src(void *dst, void *src, size_t len) +{ + if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) { + if (IS_ENABLED(CONFIG_64BIT)) + MEMCPY_AND_ZERO_SRC(u64, dst, src, len); + MEMCPY_AND_ZERO_SRC(u32, dst, src, len); + MEMCPY_AND_ZERO_SRC(u16, dst, src, len); + } + MEMCPY_AND_ZERO_SRC(u8, dst, src, len); +} + +/** + * __cvdso_getrandom_data - Generic vDSO implementation of getrandom() syscall. + * @rng_info: Describes state of kernel RNG, memory shared with kernel. + * @buffer: Destination buffer to fill with random bytes. + * @len: Size of @buffer in bytes. + * @flags: Zero or more GRND_* flags. + * @opaque_state: Pointer to an opaque state area. + * @opaque_len: Length of opaque state area. + * + * This implements a "fast key erasure" RNG using ChaCha20, in the same way that the kernel's + * getrandom() syscall does. It periodically reseeds its key from the kernel's RNG, at the same + * schedule that the kernel's RNG is reseeded. If the kernel's RNG is not ready, then this always + * calls into the syscall. + * + * @opaque_state *must* be allocated using the vgetrandom_alloc() syscall. Unless external locking + * is used, one state must be allocated per thread, as it is not safe to call this function + * concurrently with the same @opaque_state. However, it is safe to call this using the same + * @opaque_state that is shared between main code and signal handling code, within the same thread. + * + * Returns: The number of random bytes written to @buffer, or a negative value indicating an error. + */ +static __always_inline ssize_t +__cvdso_getrandom_data(const struct vdso_rng_data *rng_info, void *buffer, size_t len, + unsigned int flags, void *opaque_state, size_t opaque_len) +{ + ssize_t ret = min_t(size_t, INT_MAX & PAGE_MASK /* = MAX_RW_COUNT */, len); + struct vgetrandom_state *state = opaque_state; + size_t batch_len, nblocks, orig_len = len; + bool in_use, have_retried = false; + unsigned long current_generation; + void *orig_buffer = buffer; + u32 counter[2] = { 0 }; + + /* The state must not straddle a page, since pages can be zeroed at any time. */ + if (unlikely(((unsigned long)opaque_state & ~PAGE_MASK) + sizeof(*state) > PAGE_SIZE)) + return -EFAULT; + + /* If the caller passes the wrong size, which might happen due to CRIU, fallback. */ + if (unlikely(opaque_len != sizeof(*state))) + goto fallback_syscall; + + /* + * If the kernel's RNG is not yet ready, then it's not possible to provide random bytes from + * userspace, because A) the various @flags require this to block, or not, depending on + * various factors unavailable to userspace, and B) the kernel's behavior before the RNG is + * ready is to reseed from the entropy pool at every invocation. + */ + if (unlikely(!READ_ONCE(rng_info->is_ready))) + goto fallback_syscall; + + /* + * This condition is checked after @rng_info->is_ready, because before the kernel's RNG is + * initialized, the @flags parameter may require this to block or return an error, even when + * len is zero. + */ + if (unlikely(!len)) + return 0; + + /* + * @state->in_use is basic reentrancy protection against this running in a signal handler + * with the same @opaque_state, but obviously not atomic wrt multiple CPUs or more than one + * level of reentrancy. If a signal interrupts this after reading @state->in_use, but before + * writing @state->in_use, there is still no race, because the signal handler will run to + * its completion before returning execution. + */ + in_use = READ_ONCE(state->in_use); + if (unlikely(in_use)) + /* The syscall simply fills the buffer and does not touch @state, so fallback. */ + goto fallback_syscall; + WRITE_ONCE(state->in_use, true); + +retry_generation: + /* + * @rng_info->generation must always be read here, as it serializes @state->key with the + * kernel's RNG reseeding schedule. + */ + current_generation = READ_ONCE(rng_info->generation); + + /* + * If @state->generation doesn't match the kernel RNG's generation, then it means the + * kernel's RNG has reseeded, and so @state->key is reseeded as well. + */ + if (unlikely(state->generation != current_generation)) { + /* + * Write the generation before filling the key, in case of fork. If there is a fork + * just after this line, the parent and child will get different random bytes from + * the syscall, which is good. However, were this line to occur after the getrandom + * syscall, then both child and parent could have the same bytes and the same + * generation counter, so the fork would not be detected. Therefore, write + * @state->generation before the call to the getrandom syscall. + */ + WRITE_ONCE(state->generation, current_generation); + + /* + * Prevent the syscall from being reordered wrt current_generation. Pairs with the + * smp_store_release(&_vdso_rng_data.generation) in random.c. + */ + smp_rmb(); + + /* Reseed @state->key using fresh bytes from the kernel. */ + if (getrandom_syscall(state->key, sizeof(state->key), 0) != sizeof(state->key)) { + /* + * If the syscall failed to refresh the key, then @state->key is now + * invalid, so invalidate the generation so that it is not used again, and + * fallback to using the syscall entirely. + */ + WRITE_ONCE(state->generation, 0); + + /* + * Set @state->in_use to false only after the last write to @state in the + * line above. + */ + WRITE_ONCE(state->in_use, false); + + goto fallback_syscall; + } + + /* + * Set @state->pos to beyond the end of the batch, so that the batch is refilled + * using the new key. + */ + state->pos = sizeof(state->batch); + } + + /* Set len to the total amount of bytes that this function is allowed to read, ret. */ + len = ret; +more_batch: + /* + * First use bytes out of @state->batch, which may have been filled by the last call to this + * function. + */ + batch_len = min_t(size_t, sizeof(state->batch) - state->pos, len); + if (batch_len) { + /* Zeroing at the same time as memcpying helps preserve forward secrecy. */ + memcpy_and_zero_src(buffer, state->batch + state->pos, batch_len); + state->pos += batch_len; + buffer += batch_len; + len -= batch_len; + } + + if (!len) { + /* Prevent the loop from being reordered wrt ->generation. */ + barrier(); + + /* + * Since @rng_info->generation will never be 0, re-read @state->generation, rather + * than using the local current_generation variable, to learn whether a fork + * occurred or if @state was zeroed due to memory pressure. Primarily, though, this + * indicates whether the kernel's RNG has reseeded, in which case generate a new key + * and start over. + */ + if (unlikely(READ_ONCE(state->generation) != READ_ONCE(rng_info->generation))) { + /* + * Prevent this from looping forever in case of low memory or racing with a + * user force-reseeding the kernel's RNG using the ioctl. + */ + if (have_retried) { + WRITE_ONCE(state->in_use, false); + goto fallback_syscall; + } + + have_retried = true; + buffer = orig_buffer; + goto retry_generation; + } + + /* + * Set @state->in_use to false only when there will be no more reads or writes of + * @state. + */ + WRITE_ONCE(state->in_use, false); + return ret; + } + + /* Generate blocks of RNG output directly into @buffer while there's enough room left. */ + nblocks = len / CHACHA_BLOCK_SIZE; + if (nblocks) { + __arch_chacha20_blocks_nostack(buffer, state->key, counter, nblocks); + buffer += nblocks * CHACHA_BLOCK_SIZE; + len -= nblocks * CHACHA_BLOCK_SIZE; + } + + BUILD_BUG_ON(sizeof(state->batch_key) % CHACHA_BLOCK_SIZE != 0); + + /* Refill the batch and overwrite the key, in order to preserve forward secrecy. */ + __arch_chacha20_blocks_nostack(state->batch_key, state->key, counter, + sizeof(state->batch_key) / CHACHA_BLOCK_SIZE); + + /* Since the batch was just refilled, set the position back to 0 to indicate a full batch. */ + state->pos = 0; + goto more_batch; + +fallback_syscall: + return getrandom_syscall(orig_buffer, orig_len, flags); +} + +static __always_inline ssize_t +__cvdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len) +{ + return __cvdso_getrandom_data(__arch_get_vdso_rng_data(), buffer, len, flags, opaque_state, opaque_len); +} diff --git a/tools/testing/selftests/vDSO/.gitignore b/tools/testing/selftests/vDSO/.gitignore index a8dc51af5a9c..7dbfdec53f3d 100644 --- a/tools/testing/selftests/vDSO/.gitignore +++ b/tools/testing/selftests/vDSO/.gitignore @@ -6,3 +6,4 @@ vdso_test_correctness vdso_test_gettimeofday vdso_test_getcpu vdso_standalone_test_x86 +vdso_test_getrandom diff --git a/tools/testing/selftests/vDSO/Makefile b/tools/testing/selftests/vDSO/Makefile index d53a4d8008f9..fd7c29d9814b 100644 --- a/tools/testing/selftests/vDSO/Makefile +++ b/tools/testing/selftests/vDSO/Makefile @@ -11,9 +11,11 @@ ifeq ($(ARCH),$(filter $(ARCH),x86 x86_64)) TEST_GEN_PROGS += $(OUTPUT)/vdso_standalone_test_x86 endif TEST_GEN_PROGS += $(OUTPUT)/vdso_test_correctness +TEST_GEN_PROGS += $(OUTPUT)/vdso_test_getrandom CFLAGS := -std=gnu99 CFLAGS_vdso_standalone_test_x86 := -nostdlib -fno-asynchronous-unwind-tables -fno-stack-protector +CFLAGS_vdso_test_getrandom := -isystem $(top_srcdir)/tools/include -isystem $(top_srcdir)/include/uapi LDFLAGS_vdso_test_correctness := -ldl ifeq ($(CONFIG_X86_32),y) LDLIBS += -lgcc_s @@ -33,3 +35,5 @@ $(OUTPUT)/vdso_test_correctness: vdso_test_correctness.c vdso_test_correctness.c \ -o $@ \ $(LDFLAGS_vdso_test_correctness) +$(OUTPUT)/vdso_test_getrandom: CFLAGS += $(CFLAGS_vdso_test_getrandom) +$(OUTPUT)/vdso_test_getrandom: parse_vdso.c diff --git a/tools/testing/selftests/vDSO/vdso_test_getrandom.c b/tools/testing/selftests/vDSO/vdso_test_getrandom.c new file mode 100644 index 000000000000..2cdab4cdd152 --- /dev/null +++ b/tools/testing/selftests/vDSO/vdso_test_getrandom.c @@ -0,0 +1,296 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2022-2024 Jason A. Donenfeld . All Rights Reserved. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "../kselftest.h" +#include "parse_vdso.h" + +#ifndef timespecsub +#define timespecsub(tsp, usp, vsp) \ + do { \ + (vsp)->tv_sec = (tsp)->tv_sec - (usp)->tv_sec; \ + (vsp)->tv_nsec = (tsp)->tv_nsec - (usp)->tv_nsec; \ + if ((vsp)->tv_nsec < 0) { \ + (vsp)->tv_sec--; \ + (vsp)->tv_nsec += 1000000000L; \ + } \ + } while (0) +#endif + +static void *vgetrandom_alloc(size_t *num, size_t *size_per_each, size_t *bytes_allocated) +{ + enum { __NR_vgetrandom_alloc = 463 }; + struct vgetrandom_alloc_args args = { .num = *num }; + void *ret = (void *)syscall(__NR_vgetrandom_alloc, &args, VGETRANDOM_ALLOC_ARGS_SIZE_VER0); + if (ret != MAP_FAILED) { + *num = args.num; + *size_per_each = args.size_per_each; + *bytes_allocated = args.bytes_allocated; + } + return ret; +} + +static struct { + pthread_mutex_t lock; + void **states; + size_t len, cap, size_per_each; +} grnd_allocator = { + .lock = PTHREAD_MUTEX_INITIALIZER +}; + +static void *vgetrandom_get_state(void) +{ + void *state = NULL; + + pthread_mutex_lock(&grnd_allocator.lock); + if (!grnd_allocator.len) { + size_t page_size = getpagesize(); + size_t new_cap; + size_t bytes_allocated, size_per_each, num = sysconf(_SC_NPROCESSORS_ONLN); /* Just a decent heuristic. */ + void *new_block = vgetrandom_alloc(&num, &size_per_each, &bytes_allocated); + void *new_states; + + if (new_block == MAP_FAILED) + goto out; + if (grnd_allocator.size_per_each && grnd_allocator.size_per_each != size_per_each) + goto unmap; + grnd_allocator.size_per_each = size_per_each; + new_cap = grnd_allocator.cap + num; + new_states = reallocarray(grnd_allocator.states, new_cap, sizeof(*grnd_allocator.states)); + if (!new_states) + goto unmap; + grnd_allocator.cap = new_cap; + grnd_allocator.states = new_states; + + for (size_t i = 0; i < num; ++i) { + grnd_allocator.states[i] = new_block; + if (((uintptr_t)new_block & (page_size - 1)) + size_per_each > page_size) + new_block = (void *)(((uintptr_t)new_block + page_size) & (page_size - 1)); + else + new_block += size_per_each; + } + grnd_allocator.len = num; + goto success; + + unmap: + munmap(new_block, bytes_allocated); + goto out; + } +success: + state = grnd_allocator.states[--grnd_allocator.len]; + +out: + pthread_mutex_unlock(&grnd_allocator.lock); + return state; +} + +static void vgetrandom_put_state(void *state) +{ + if (!state) + return; + pthread_mutex_lock(&grnd_allocator.lock); + grnd_allocator.states[grnd_allocator.len++] = state; + pthread_mutex_unlock(&grnd_allocator.lock); +} + +static struct { + ssize_t(*fn)(void *, size_t, unsigned long, void *, size_t); + pthread_key_t key; + pthread_once_t initialized; +} grnd_ctx = { + .initialized = PTHREAD_ONCE_INIT +}; + +static void vgetrandom_init(void) +{ + if (pthread_key_create(&grnd_ctx.key, vgetrandom_put_state) != 0) + return; + unsigned long sysinfo_ehdr = getauxval(AT_SYSINFO_EHDR); + if (!sysinfo_ehdr) { + printf("AT_SYSINFO_EHDR is not present!\n"); + exit(KSFT_SKIP); + } + vdso_init_from_sysinfo_ehdr(sysinfo_ehdr); + grnd_ctx.fn = (__typeof__(grnd_ctx.fn))vdso_sym("LINUX_2.6", "__vdso_getrandom"); + if (!grnd_ctx.fn) { + printf("__vdso_getrandom is missing!\n"); + exit(KSFT_FAIL); + } +} + +static ssize_t vgetrandom(void *buf, size_t len, unsigned long flags) +{ + void *state; + + pthread_once(&grnd_ctx.initialized, vgetrandom_init); + state = pthread_getspecific(grnd_ctx.key); + if (!state) { + state = vgetrandom_get_state(); + if (pthread_setspecific(grnd_ctx.key, state) != 0) { + vgetrandom_put_state(state); + state = NULL; + } + if (!state) { + printf("vgetrandom_get_state failed!\n"); + exit(KSFT_FAIL); + } + } + return grnd_ctx.fn(buf, len, flags, state, grnd_allocator.size_per_each); +} + +enum { TRIALS = 25000000, THREADS = 256 }; + +static void *test_vdso_getrandom(void *) +{ + for (size_t i = 0; i < TRIALS; ++i) { + unsigned int val; + ssize_t ret = vgetrandom(&val, sizeof(val), 0); + assert(ret == sizeof(val)); + } + return NULL; +} + +static void *test_libc_getrandom(void *) +{ + for (size_t i = 0; i < TRIALS; ++i) { + unsigned int val; + ssize_t ret = getrandom(&val, sizeof(val), 0); + assert(ret == sizeof(val)); + } + return NULL; +} + +static void *test_syscall_getrandom(void *) +{ + for (size_t i = 0; i < TRIALS; ++i) { + unsigned int val; + ssize_t ret = syscall(SYS_getrandom, &val, sizeof(val), 0); + assert(ret == sizeof(val)); + } + return NULL; +} + +static void bench_single(void) +{ + struct timespec start, end, diff; + + clock_gettime(CLOCK_MONOTONIC, &start); + test_vdso_getrandom(NULL); + clock_gettime(CLOCK_MONOTONIC, &end); + timespecsub(&end, &start, &diff); + printf(" vdso: %u times in %lu.%09lu seconds\n", TRIALS, diff.tv_sec, diff.tv_nsec); + + clock_gettime(CLOCK_MONOTONIC, &start); + test_libc_getrandom(NULL); + clock_gettime(CLOCK_MONOTONIC, &end); + timespecsub(&end, &start, &diff); + printf(" libc: %u times in %lu.%09lu seconds\n", TRIALS, diff.tv_sec, diff.tv_nsec); + + clock_gettime(CLOCK_MONOTONIC, &start); + test_syscall_getrandom(NULL); + clock_gettime(CLOCK_MONOTONIC, &end); + timespecsub(&end, &start, &diff); + printf("syscall: %u times in %lu.%09lu seconds\n", TRIALS, diff.tv_sec, diff.tv_nsec); +} + +static void bench_multi(void) +{ + struct timespec start, end, diff; + pthread_t threads[THREADS]; + + clock_gettime(CLOCK_MONOTONIC, &start); + for (size_t i = 0; i < THREADS; ++i) + assert(pthread_create(&threads[i], NULL, test_vdso_getrandom, NULL) == 0); + for (size_t i = 0; i < THREADS; ++i) + pthread_join(threads[i], NULL); + clock_gettime(CLOCK_MONOTONIC, &end); + timespecsub(&end, &start, &diff); + printf(" vdso: %u x %u times in %lu.%09lu seconds\n", TRIALS, THREADS, diff.tv_sec, diff.tv_nsec); + + clock_gettime(CLOCK_MONOTONIC, &start); + for (size_t i = 0; i < THREADS; ++i) + assert(pthread_create(&threads[i], NULL, test_libc_getrandom, NULL) == 0); + for (size_t i = 0; i < THREADS; ++i) + pthread_join(threads[i], NULL); + clock_gettime(CLOCK_MONOTONIC, &end); + timespecsub(&end, &start, &diff); + printf(" libc: %u x %u times in %lu.%09lu seconds\n", TRIALS, THREADS, diff.tv_sec, diff.tv_nsec); + + clock_gettime(CLOCK_MONOTONIC, &start); + for (size_t i = 0; i < THREADS; ++i) + assert(pthread_create(&threads[i], NULL, test_syscall_getrandom, NULL) == 0); + for (size_t i = 0; i < THREADS; ++i) + pthread_join(threads[i], NULL); + clock_gettime(CLOCK_MONOTONIC, &end); + timespecsub(&end, &start, &diff); + printf(" syscall: %u x %u times in %lu.%09lu seconds\n", TRIALS, THREADS, diff.tv_sec, diff.tv_nsec); +} + +static void fill(void) +{ + uint8_t weird_size[323929]; + for (;;) + vgetrandom(weird_size, sizeof(weird_size), 0); +} + +static void kselftest(void) +{ + uint8_t weird_size[1263]; + + ksft_print_header(); + ksft_set_plan(1); + + for (size_t i = 0; i < 1000; ++i) { + ssize_t ret = vgetrandom(weird_size, sizeof(weird_size), 0); + if (ret != sizeof(weird_size)) + exit(KSFT_FAIL); + } + + ksft_test_result_pass("getrandom: PASS\n"); + exit(KSFT_PASS); +} + +static void usage(const char *argv0) +{ + fprintf(stderr, "Usage: %s [bench-single|bench-multi|fill]\n", argv0); +} + +int main(int argc, char *argv[]) +{ + if (argc == 1) { + kselftest(); + return 0; + } + + if (argc != 2) { + usage(argv[0]); + return 1; + } + if (!strcmp(argv[1], "bench-single")) + bench_single(); + else if (!strcmp(argv[1], "bench-multi")) + bench_multi(); + else if (!strcmp(argv[1], "fill")) + fill(); + else { + usage(argv[0]); + return 1; + } + return 0; +} From patchwork Mon Jul 1 13:57:59 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Jason A. Donenfeld" X-Patchwork-Id: 13718180 X-Patchwork-Delegate: herbert@gondor.apana.org.au Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 415E316088F; Mon, 1 Jul 2024 13:58:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842315; cv=none; b=QA6vZjzx5ZmjejW+fWc4+GfN4ceSTy0dTCJmmOXujgVzXlZVDiHYkvPDOlPSTnLFaNOHS+FgsVqbdAvNym6uXr2HrvZ4wC+9WPXYknfSOZsoFTqeGZ3XZ0uh3/mR9cOjs9EaPzzOPtPVBZDEX7zbhcfkUQ7hE93xbIMsVI37zLY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719842315; c=relaxed/simple; bh=hIYliNLqZI2ldS70zWMwb+m8+iUUvJJcHCXl5wmJquM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=o/os7dOunZEbdTWS9JPBrNaWiRMrJyWvXoenumXznphwAXsdSkLmwUAxlIKOYNT2gjUOPJUpfL4wORZ4pewIcYokurIkqGlHGp43DV7UrGH53a9orRSLVo741tIYEuu8L7gEHLdeNgVcWVmjINX5aGWKfODkpNH3mzGjGXxVf50= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b=MNC7Aq6Q; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="MNC7Aq6Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F7D6C32786; Mon, 1 Jul 2024 13:58:33 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="MNC7Aq6Q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1719842312; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oxgtpEvzDDXyCwVnCoI3IOMUP2jkl9OOIZCyMvex310=; b=MNC7Aq6Q3STAfWc/0ozEOXED7qbNo+QDXon7PPphGoZhW2X7fqYIHZNs06StZ3HX44QW5R I1Qak+I2AaQAGwMKzm6vgBGgN1cqxKb6ttpZw6LEvxBw3x4zxQ2sqZTzm1eNINE8s+Efx2 /Qz6qXlnTHrDNXMWPZbWCLzQrEKJoeE= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id f4843f23 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Mon, 1 Jul 2024 13:58:32 +0000 (UTC) From: "Jason A. Donenfeld" To: linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de Cc: "Jason A. Donenfeld" , linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand , Samuel Neves Subject: [PATCH v19 5/5] x86: vdso: Wire up getrandom() vDSO implementation Date: Mon, 1 Jul 2024 15:57:59 +0200 Message-ID: <20240701135801.3698-6-Jason@zx2c4.com> In-Reply-To: <20240701135801.3698-1-Jason@zx2c4.com> References: <20240701135801.3698-1-Jason@zx2c4.com> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Hook up the generic vDSO implementation to the x86 vDSO data page. Since the existing vDSO infrastructure is heavily based on the timekeeping functionality, which works over arrays of bases, a new macro is introduced for vvars that are not arrays. The vDSO function requires a ChaCha20 implementation that does not write to the stack, yet can still do an entire ChaCha20 permutation, so provide this using SSE2, since this is userland code that must work on all x86-64 processors. There's a simple test for this code as well. Reviewed-by: Thomas Gleixner Reviewed-by: Samuel Neves # for vgetrandom-chacha.S Signed-off-by: Jason A. Donenfeld --- arch/x86/Kconfig | 1 + arch/x86/entry/vdso/Makefile | 3 +- arch/x86/entry/vdso/vdso.lds.S | 2 + arch/x86/entry/vdso/vgetrandom-chacha.S | 178 ++++++++++++++++++ arch/x86/entry/vdso/vgetrandom.c | 17 ++ arch/x86/include/asm/vdso/getrandom.h | 55 ++++++ arch/x86/include/asm/vdso/vsyscall.h | 2 + arch/x86/include/asm/vvar.h | 16 ++ tools/testing/selftests/vDSO/.gitignore | 1 + tools/testing/selftests/vDSO/Makefile | 15 ++ .../testing/selftests/vDSO/vdso_test_chacha.c | 43 +++++ 11 files changed, 332 insertions(+), 1 deletion(-) create mode 100644 arch/x86/entry/vdso/vgetrandom-chacha.S create mode 100644 arch/x86/entry/vdso/vgetrandom.c create mode 100644 arch/x86/include/asm/vdso/getrandom.h create mode 100644 tools/testing/selftests/vDSO/vdso_test_chacha.c diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1d7122a1883e..9c98b7a88cc2 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -287,6 +287,7 @@ config X86 select HAVE_UNSTABLE_SCHED_CLOCK select HAVE_USER_RETURN_NOTIFIER select HAVE_GENERIC_VDSO + select VDSO_GETRANDOM if X86_64 select HOTPLUG_PARALLEL if SMP && X86_64 select HOTPLUG_SMT if SMP select HOTPLUG_SPLIT_STARTUP if SMP && X86_32 diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index 215a1b202a91..c9216ac4fb1e 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -7,7 +7,7 @@ include $(srctree)/lib/vdso/Makefile # Files to link into the vDSO: -vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o +vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o vgetrandom.o vgetrandom-chacha.o vobjs32-y := vdso32/note.o vdso32/system_call.o vdso32/sigreturn.o vobjs32-y += vdso32/vclock_gettime.o vdso32/vgetcpu.o vobjs-$(CONFIG_X86_SGX) += vsgx.o @@ -73,6 +73,7 @@ CFLAGS_REMOVE_vdso32/vclock_gettime.o = -pg CFLAGS_REMOVE_vgetcpu.o = -pg CFLAGS_REMOVE_vdso32/vgetcpu.o = -pg CFLAGS_REMOVE_vsgx.o = -pg +CFLAGS_REMOVE_vgetrandom.o = -pg # # X32 processes use x32 vDSO to access 64bit kernel data. diff --git a/arch/x86/entry/vdso/vdso.lds.S b/arch/x86/entry/vdso/vdso.lds.S index e8c60ae7a7c8..0bab5f4af6d1 100644 --- a/arch/x86/entry/vdso/vdso.lds.S +++ b/arch/x86/entry/vdso/vdso.lds.S @@ -30,6 +30,8 @@ VERSION { #ifdef CONFIG_X86_SGX __vdso_sgx_enter_enclave; #endif + getrandom; + __vdso_getrandom; local: *; }; } diff --git a/arch/x86/entry/vdso/vgetrandom-chacha.S b/arch/x86/entry/vdso/vgetrandom-chacha.S new file mode 100644 index 000000000000..bcba5639b8ee --- /dev/null +++ b/arch/x86/entry/vdso/vgetrandom-chacha.S @@ -0,0 +1,178 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2022-2024 Jason A. Donenfeld . All Rights Reserved. + */ + +#include +#include + +.section .rodata, "a" +.align 16 +CONSTANTS: .octa 0x6b20657479622d323320646e61707865 +.text + +/* + * Very basic SSE2 implementation of ChaCha20. Produces a given positive number + * of blocks of output with a nonce of 0, taking an input key and 8-byte + * counter. Importantly does not spill to the stack. Its arguments are: + * + * rdi: output bytes + * rsi: 32-byte key input + * rdx: 8-byte counter input/output + * rcx: number of 64-byte blocks to write to output + */ +SYM_FUNC_START(__arch_chacha20_blocks_nostack) + +.set output, %rdi +.set key, %rsi +.set counter, %rdx +.set nblocks, %rcx +.set i, %al +/* xmm registers are *not* callee-save. */ +.set temp, %xmm0 +.set state0, %xmm1 +.set state1, %xmm2 +.set state2, %xmm3 +.set state3, %xmm4 +.set copy0, %xmm5 +.set copy1, %xmm6 +.set copy2, %xmm7 +.set copy3, %xmm8 +.set one, %xmm9 + + /* copy0 = "expand 32-byte k" */ + movaps CONSTANTS(%rip),copy0 + /* copy1,copy2 = key */ + movups 0x00(key),copy1 + movups 0x10(key),copy2 + /* copy3 = counter || zero nonce */ + movq 0x00(counter),copy3 + /* one = 1 || 0 */ + movq $1,%rax + movq %rax,one + +.Lblock: + /* state0,state1,state2,state3 = copy0,copy1,copy2,copy3 */ + movdqa copy0,state0 + movdqa copy1,state1 + movdqa copy2,state2 + movdqa copy3,state3 + + movb $10,i +.Lpermute: + /* state0 += state1, state3 = rotl32(state3 ^ state0, 16) */ + paddd state1,state0 + pxor state0,state3 + movdqa state3,temp + pslld $16,temp + psrld $16,state3 + por temp,state3 + + /* state2 += state3, state1 = rotl32(state1 ^ state2, 12) */ + paddd state3,state2 + pxor state2,state1 + movdqa state1,temp + pslld $12,temp + psrld $20,state1 + por temp,state1 + + /* state0 += state1, state3 = rotl32(state3 ^ state0, 8) */ + paddd state1,state0 + pxor state0,state3 + movdqa state3,temp + pslld $8,temp + psrld $24,state3 + por temp,state3 + + /* state2 += state3, state1 = rotl32(state1 ^ state2, 7) */ + paddd state3,state2 + pxor state2,state1 + movdqa state1,temp + pslld $7,temp + psrld $25,state1 + por temp,state1 + + /* state1[0,1,2,3] = state1[1,2,3,0] */ + pshufd $0x39,state1,state1 + /* state2[0,1,2,3] = state2[2,3,0,1] */ + pshufd $0x4e,state2,state2 + /* state3[0,1,2,3] = state3[3,0,1,2] */ + pshufd $0x93,state3,state3 + + /* state0 += state1, state3 = rotl32(state3 ^ state0, 16) */ + paddd state1,state0 + pxor state0,state3 + movdqa state3,temp + pslld $16,temp + psrld $16,state3 + por temp,state3 + + /* state2 += state3, state1 = rotl32(state1 ^ state2, 12) */ + paddd state3,state2 + pxor state2,state1 + movdqa state1,temp + pslld $12,temp + psrld $20,state1 + por temp,state1 + + /* state0 += state1, state3 = rotl32(state3 ^ state0, 8) */ + paddd state1,state0 + pxor state0,state3 + movdqa state3,temp + pslld $8,temp + psrld $24,state3 + por temp,state3 + + /* state2 += state3, state1 = rotl32(state1 ^ state2, 7) */ + paddd state3,state2 + pxor state2,state1 + movdqa state1,temp + pslld $7,temp + psrld $25,state1 + por temp,state1 + + /* state1[0,1,2,3] = state1[3,0,1,2] */ + pshufd $0x93,state1,state1 + /* state2[0,1,2,3] = state2[2,3,0,1] */ + pshufd $0x4e,state2,state2 + /* state3[0,1,2,3] = state3[1,2,3,0] */ + pshufd $0x39,state3,state3 + + decb i + jnz .Lpermute + + /* output0 = state0 + copy0 */ + paddd copy0,state0 + movups state0,0x00(output) + /* output1 = state1 + copy1 */ + paddd copy1,state1 + movups state1,0x10(output) + /* output2 = state2 + copy2 */ + paddd copy2,state2 + movups state2,0x20(output) + /* output3 = state3 + copy3 */ + paddd copy3,state3 + movups state3,0x30(output) + + /* ++copy3.counter */ + paddq one,copy3 + + /* output += 64, --nblocks */ + addq $64,output + decq nblocks + jnz .Lblock + + /* counter = copy3.counter */ + movq copy3,0x00(counter) + + /* Zero out the potentially sensitive regs, in case nothing uses these again. */ + pxor state0,state0 + pxor state1,state1 + pxor state2,state2 + pxor state3,state3 + pxor copy1,copy1 + pxor copy2,copy2 + pxor temp,temp + + ret +SYM_FUNC_END(__arch_chacha20_blocks_nostack) diff --git a/arch/x86/entry/vdso/vgetrandom.c b/arch/x86/entry/vdso/vgetrandom.c new file mode 100644 index 000000000000..52d3c7faae2e --- /dev/null +++ b/arch/x86/entry/vdso/vgetrandom.c @@ -0,0 +1,17 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2022-2024 Jason A. Donenfeld . All Rights Reserved. + */ +#include + +#include "../../../../lib/vdso/getrandom.c" + +ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len); + +ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len) +{ + return __cvdso_getrandom(buffer, len, flags, opaque_state, opaque_len); +} + +ssize_t getrandom(void *, size_t, unsigned int, void *, size_t) + __attribute__((weak, alias("__vdso_getrandom"))); diff --git a/arch/x86/include/asm/vdso/getrandom.h b/arch/x86/include/asm/vdso/getrandom.h new file mode 100644 index 000000000000..b96e674cafde --- /dev/null +++ b/arch/x86/include/asm/vdso/getrandom.h @@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2022-2024 Jason A. Donenfeld . All Rights Reserved. + */ +#ifndef __ASM_VDSO_GETRANDOM_H +#define __ASM_VDSO_GETRANDOM_H + +#ifndef __ASSEMBLY__ + +#include +#include + +/** + * getrandom_syscall - Invoke the getrandom() syscall. + * @buffer: Destination buffer to fill with random bytes. + * @len: Size of @buffer in bytes. + * @flags: Zero or more GRND_* flags. + * Returns: The number of random bytes written to @buffer, or a negative value indicating an error. + */ +static __always_inline ssize_t getrandom_syscall(void *buffer, size_t len, unsigned int flags) +{ + long ret; + + asm ("syscall" : "=a" (ret) : + "0" (__NR_getrandom), "D" (buffer), "S" (len), "d" (flags) : + "rcx", "r11", "memory"); + + return ret; +} + +#define __vdso_rng_data (VVAR(_vdso_rng_data)) + +static __always_inline const struct vdso_rng_data *__arch_get_vdso_rng_data(void) +{ + if (IS_ENABLED(CONFIG_TIME_NS) && __vdso_data->clock_mode == VDSO_CLOCKMODE_TIMENS) + return (void *)&__vdso_rng_data + ((void *)&__timens_vdso_data - (void *)&__vdso_data); + return &__vdso_rng_data; +} + +/** + * __arch_chacha20_blocks_nostack - Generate ChaCha20 stream without using the stack. + * @dst_bytes: Destination buffer to hold @nblocks * 64 bytes of output. + * @key: 32-byte input key. + * @counter: 8-byte counter, read on input and updated on return. + * @nblocks: Number of blocks to generate. + * + * Generates a given positive number of blocks of ChaCha20 output with nonce=0, and does not write + * to any stack or memory outside of the parameters passed to it, in order to mitigate stack data + * leaking into forked child processes. + */ +extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks); + +#endif /* !__ASSEMBLY__ */ + +#endif /* __ASM_VDSO_GETRANDOM_H */ diff --git a/arch/x86/include/asm/vdso/vsyscall.h b/arch/x86/include/asm/vdso/vsyscall.h index be199a9b2676..71c56586a22f 100644 --- a/arch/x86/include/asm/vdso/vsyscall.h +++ b/arch/x86/include/asm/vdso/vsyscall.h @@ -11,6 +11,8 @@ #include DEFINE_VVAR(struct vdso_data, _vdso_data); +DEFINE_VVAR_SINGLE(struct vdso_rng_data, _vdso_rng_data); + /* * Update the vDSO data page to keep in sync with kernel timekeeping. */ diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h index 183e98e49ab9..9d9af37f7cab 100644 --- a/arch/x86/include/asm/vvar.h +++ b/arch/x86/include/asm/vvar.h @@ -26,6 +26,8 @@ */ #define DECLARE_VVAR(offset, type, name) \ EMIT_VVAR(name, offset) +#define DECLARE_VVAR_SINGLE(offset, type, name) \ + EMIT_VVAR(name, offset) #else @@ -37,6 +39,10 @@ extern char __vvar_page; extern type timens_ ## name[CS_BASES] \ __attribute__((visibility("hidden"))); \ +#define DECLARE_VVAR_SINGLE(offset, type, name) \ + extern type vvar_ ## name \ + __attribute__((visibility("hidden"))); \ + #define VVAR(name) (vvar_ ## name) #define TIMENS(name) (timens_ ## name) @@ -44,12 +50,22 @@ extern char __vvar_page; type name[CS_BASES] \ __attribute__((section(".vvar_" #name), aligned(16))) __visible +#define DEFINE_VVAR_SINGLE(type, name) \ + type name \ + __attribute__((section(".vvar_" #name), aligned(16))) __visible + #endif /* DECLARE_VVAR(offset, type, name) */ DECLARE_VVAR(128, struct vdso_data, _vdso_data) +#if !defined(_SINGLE_DATA) +#define _SINGLE_DATA +DECLARE_VVAR_SINGLE(640, struct vdso_rng_data, _vdso_rng_data) +#endif + #undef DECLARE_VVAR +#undef DECLARE_VVAR_SINGLE #endif diff --git a/tools/testing/selftests/vDSO/.gitignore b/tools/testing/selftests/vDSO/.gitignore index 7dbfdec53f3d..30d5c8f0e5c7 100644 --- a/tools/testing/selftests/vDSO/.gitignore +++ b/tools/testing/selftests/vDSO/.gitignore @@ -7,3 +7,4 @@ vdso_test_gettimeofday vdso_test_getcpu vdso_standalone_test_x86 vdso_test_getrandom +vdso_test_chacha diff --git a/tools/testing/selftests/vDSO/Makefile b/tools/testing/selftests/vDSO/Makefile index fd7c29d9814b..f828e0a9d498 100644 --- a/tools/testing/selftests/vDSO/Makefile +++ b/tools/testing/selftests/vDSO/Makefile @@ -3,6 +3,7 @@ include ../lib.mk uname_M := $(shell uname -m 2>/dev/null || echo not) ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/) +SODIUM := $(shell pkg-config --libs libsodium 2>/dev/null) TEST_GEN_PROGS := $(OUTPUT)/vdso_test_gettimeofday $(OUTPUT)/vdso_test_getcpu TEST_GEN_PROGS += $(OUTPUT)/vdso_test_abi @@ -12,10 +13,18 @@ TEST_GEN_PROGS += $(OUTPUT)/vdso_standalone_test_x86 endif TEST_GEN_PROGS += $(OUTPUT)/vdso_test_correctness TEST_GEN_PROGS += $(OUTPUT)/vdso_test_getrandom +ifeq ($(uname_M),x86_64) +ifneq ($(SODIUM),) +TEST_GEN_PROGS += $(OUTPUT)/vdso_test_chacha +endif +endif CFLAGS := -std=gnu99 CFLAGS_vdso_standalone_test_x86 := -nostdlib -fno-asynchronous-unwind-tables -fno-stack-protector CFLAGS_vdso_test_getrandom := -isystem $(top_srcdir)/tools/include -isystem $(top_srcdir)/include/uapi +CFLAGS_vdso_test_chacha := $(SODIUM) -idirafter $(top_srcdir)/include -idirafter \ + $(top_srcdir)/arch/$(ARCH)/include -idirafter include \ + -D__ASSEMBLY__ -DBULID_VDSO -DCONFIG_FUNCTION_ALIGNMENT=0 -Wa,--noexecstack LDFLAGS_vdso_test_correctness := -ldl ifeq ($(CONFIG_X86_32),y) LDLIBS += -lgcc_s @@ -37,3 +46,9 @@ $(OUTPUT)/vdso_test_correctness: vdso_test_correctness.c $(LDFLAGS_vdso_test_correctness) $(OUTPUT)/vdso_test_getrandom: CFLAGS += $(CFLAGS_vdso_test_getrandom) $(OUTPUT)/vdso_test_getrandom: parse_vdso.c +$(OUTPUT)/vdso_test_chacha: CFLAGS += $(CFLAGS_vdso_test_chacha) +$(OUTPUT)/vdso_test_chacha: $(top_srcdir)/arch/$(ARCH)/entry/vdso/vgetrandom-chacha.S +$(OUTPUT)/vdso_test_chacha: include/asm/rwonce.h +include/asm/rwonce.h: + mkdir -p include/asm + touch $@ diff --git a/tools/testing/selftests/vDSO/vdso_test_chacha.c b/tools/testing/selftests/vDSO/vdso_test_chacha.c new file mode 100644 index 000000000000..e38f44e5f803 --- /dev/null +++ b/tools/testing/selftests/vDSO/vdso_test_chacha.c @@ -0,0 +1,43 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2022-2024 Jason A. Donenfeld . All Rights Reserved. + */ + +#include +#include +#include +#include +#include "../kselftest.h" + +extern void __arch_chacha20_blocks_nostack(uint8_t *dst_bytes, const uint8_t *key, uint32_t *counter, size_t nblocks); + +int main(int argc, char *argv[]) +{ + enum { TRIALS = 1000, BLOCKS = 128, BLOCK_SIZE = 64 }; + static const uint8_t nonce[8] = { 0 }; + uint32_t counter[2]; + uint8_t key[32]; + uint8_t output1[BLOCK_SIZE * BLOCKS], output2[BLOCK_SIZE * BLOCKS]; + + ksft_print_header(); + ksft_set_plan(1); + + for (unsigned int trial = 0; trial < TRIALS; ++trial) { + if (getrandom(key, sizeof(key), 0) != sizeof(key)) { + printf("getrandom() failed!\n"); + return KSFT_SKIP; + } + crypto_stream_chacha20(output1, sizeof(output1), nonce, key); + for (unsigned int split = 0; split < BLOCKS; ++split) { + memset(output2, 'X', sizeof(output2)); + memset(counter, 0, sizeof(counter)); + if (split) + __arch_chacha20_blocks_nostack(output2, key, counter, split); + __arch_chacha20_blocks_nostack(output2 + split * BLOCK_SIZE, key, counter, BLOCKS - split); + if (memcmp(output1, output2, sizeof(output1))) + return KSFT_FAIL; + } + } + ksft_test_result_pass("chacha: PASS\n"); + return KSFT_PASS; +}