From patchwork Tue Nov 23 05:16:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Collingbourne X-Patchwork-Id: 12693406 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CD881C433F5 for ; Tue, 23 Nov 2021 05:19:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:References: Mime-Version:Message-Id:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=Ys7vQ+VC5qqxBMUh/e9ExFWdr7PEfQDqcBx01i7r1rI=; b=HEMmUQ6Pm2sfJ9cBawX3Jz8Heh I/ZEDV3SCS2y314lWXnuJyVPVhzZleVqigM8UovXzYuwVCsK9hSX3frx26b9rrSwe4f8RE1W10H3v nY42oPZylJplHtPyoMe36rhKPjKikHZVuER23FlEsXmSgcyKOLspWnd2NHLcE5Vtdh1zb2LTtO4HS 9mkirIesNMFWcZY4unUfJc1i0PnIcZjg4YVnA2GJRZr0zubBgLlxNMCQSIgN4vsGsbMj/Zp91vKJR Bl7oGx0rmWpYeOu0sglcxga0ShDyX7BMmjZxnTjsnaUiW3+O4U+ayNGBffFe1F0X7ueYJrj70Z6Hu I6CKOXBA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mpOBq-000q0m-0h; Tue, 23 Nov 2021 05:17:58 +0000 Received: from mail-pl1-x64a.google.com ([2607:f8b0:4864:20::64a]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mpOB7-000pks-Vn for linux-arm-kernel@lists.infradead.org; Tue, 23 Nov 2021 05:17:18 +0000 Received: by mail-pl1-x64a.google.com with SMTP id p3-20020a170903248300b00143c00a5411so8549142plw.12 for ; Mon, 22 Nov 2021 21:17:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=TQIf/OIUVwGkxbYI32rejLRLSDrVm5MLPR+mboxvR5U=; b=IyYqQYg4PxGSfKhIUCW7Qqb/DNY9bL7t85jnFiptJc/PIfBvsajpLCYGW/v6AGJDQH QerrpOLxdhCfzAG7MreMDfB/QIjytpjf4wAjAk49eGwGmH4Jte3FKnbu3x8DIv2kEKvc DtPARbNm04SIS3LvipxKb5tJCgGozzXoLrNfkUp1l8PPlj+CtnS2Xi5vnE6TxQs9xkCO xU7PEtR7PBCvc7tR9NTUiscw0Mzty6cNlHB/gVrW8QVu0X+ERlC15WHbYTClfbL1csmE bUUKMvA7WLt8hbX6SQGFL+w4sxjGpmCjMsgsWRZUTDS7E/fy+ptRbfBWxxurL/NDjSql HqXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=TQIf/OIUVwGkxbYI32rejLRLSDrVm5MLPR+mboxvR5U=; b=ltiKmjL0uJIIV41EDPyUDEQuuQJQYHZD8Qr6gb7Os0zN2M0YS3/oAVq0duWZRbCE9x 7wCB5mB3WAb4u9Zg/4rULno6USTCUuBLy1EHqCvKWNl+5k5fBpyce6mi/xeeGYO1QVzz blM8qiyC0kTuGFi3epwLP1ZFdvqxjUCXRbOX61550zY5auaxCEpEHL2cQNApISW2AIv5 yorr25HlEkI208OUqgQSaviwU01TbEP2jOsdsUWElK8yWl4mWOApr267UfTrP3kHMRdE cHD5px6BOCRpCsyNohdsJWp2X4dQt+pQIMhRbnhLuYkNRjbjI6s7FtiJR2xGKTrCBuIP g+cA== X-Gm-Message-State: AOAM531oUFJ+JaAXG5+tF2hyVxJHJhIaTDp3gjlVJKSJRV7ck2FGAgky 2jgEql64Ll/Ui+FeaqhGiLeF42s= X-Google-Smtp-Source: ABdhPJwlLZKO/n9a2aoJ8uvvHMB0+nvlxyQ3QG3hLOgWLW5DUO4ylwv7GNhUmxqFZnNLsSzYO7Z4E5I= X-Received: from pcc-desktop.svl.corp.google.com ([2620:15c:2ce:200:a876:2e6a:b5f:3d90]) (user=pcc job=sendgmr) by 2002:a05:6a00:2181:b0:44c:f4bc:2f74 with SMTP id h1-20020a056a00218100b0044cf4bc2f74mr2505169pfi.68.1637644630354; Mon, 22 Nov 2021 21:17:10 -0800 (PST) Date: Mon, 22 Nov 2021 21:16:55 -0800 In-Reply-To: <20211123051658.3195589-1-pcc@google.com> Message-Id: <20211123051658.3195589-3-pcc@google.com> Mime-Version: 1.0 References: <20211123051658.3195589-1-pcc@google.com> X-Mailer: git-send-email 2.34.0.rc2.393.gf8c9666880-goog Subject: [PATCH v2 2/5] uaccess-buffer: add core code From: Peter Collingbourne To: Catalin Marinas , Will Deacon , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Thomas Gleixner , Andy Lutomirski , Kees Cook , Andrew Morton , Masahiro Yamada , Sami Tolvanen , YiFei Zhu , Colin Ian King , Mark Rutland , Frederic Weisbecker , Viresh Kumar , Andrey Konovalov , Peter Collingbourne , Gabriel Krisman Bertazi , Chris Hyser , Daniel Vetter , Chris Wilson , Arnd Bergmann , Dmitry Vyukov , Christian Brauner , "Eric W. Biederman" , Alexey Gladkov , Ran Xiaokai , David Hildenbrand , Xiaofeng Cao , Cyrill Gorcunov , Thomas Cedeno , Marco Elver , Alexander Potapenko Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Evgenii Stepanov X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211122_211714_105939_92154553 X-CRM114-Status: GOOD ( 33.69 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add the core code to support uaccess logging. Subsequent patches will hook this up to the arch-specific kernel entry and exit code for certain architectures. Link: https://linux-review.googlesource.com/id/I6581765646501a5631b281d670903945ebadc57d Signed-off-by: Peter Collingbourne --- v2: - New interface that avoids multiple syscalls per real syscall and is arch-generic - Avoid logging uaccesses done by BPF programs - Add documentation - Split up into multiple patches - Various code moves, renames etc as requested by Marco arch/Kconfig | 5 + fs/exec.c | 2 + include/linux/instrumented.h | 5 +- include/linux/sched.h | 4 + include/linux/uaccess-buffer-log-hooks.h | 59 +++++++++++ include/linux/uaccess-buffer.h | 79 ++++++++++++++ include/uapi/linux/prctl.h | 3 + include/uapi/linux/uaccess-buffer.h | 25 +++++ kernel/Makefile | 1 + kernel/bpf/helpers.c | 6 +- kernel/fork.c | 3 + kernel/signal.c | 4 +- kernel/sys.c | 6 ++ kernel/uaccess-buffer.c | 125 +++++++++++++++++++++++ 14 files changed, 324 insertions(+), 3 deletions(-) create mode 100644 include/linux/uaccess-buffer-log-hooks.h create mode 100644 include/linux/uaccess-buffer.h create mode 100644 include/uapi/linux/uaccess-buffer.h create mode 100644 kernel/uaccess-buffer.c diff --git a/arch/Kconfig b/arch/Kconfig index 26b8ed11639d..6030298a7e9a 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1302,6 +1302,11 @@ config ARCH_HAS_PARANOID_L1D_FLUSH config DYNAMIC_SIGFRAME bool +config HAVE_ARCH_UACCESS_BUFFER + bool + help + Select if the architecture's syscall entry/exit code supports uaccess buffers. + source "kernel/gcov/Kconfig" source "scripts/gcc-plugins/Kconfig" diff --git a/fs/exec.c b/fs/exec.c index 537d92c41105..5f30314f3ec6 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -65,6 +65,7 @@ #include #include #include +#include #include #include @@ -1313,6 +1314,7 @@ int begin_new_exec(struct linux_binprm * bprm) me->personality &= ~bprm->per_clear; clear_syscall_work_syscall_user_dispatch(me); + uaccess_buffer_set_descriptor_addr_addr(0); /* * We have to apply CLOEXEC before we change whether the process is diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h index 42faebbaa202..c96be1695614 100644 --- a/include/linux/instrumented.h +++ b/include/linux/instrumented.h @@ -2,7 +2,7 @@ /* * This header provides generic wrappers for memory access instrumentation that - * the compiler cannot emit for: KASAN, KCSAN. + * the compiler cannot emit for: KASAN, KCSAN, uaccess buffers. */ #ifndef _LINUX_INSTRUMENTED_H #define _LINUX_INSTRUMENTED_H @@ -11,6 +11,7 @@ #include #include #include +#include /** * instrument_read - instrument regular read access @@ -117,6 +118,7 @@ instrument_copy_to_user(void __user *to, const void *from, unsigned long n) { kasan_check_read(from, n); kcsan_check_read(from, n); + uaccess_buffer_log_write(to, n); } /** @@ -134,6 +136,7 @@ instrument_copy_from_user(const void *to, const void __user *from, unsigned long { kasan_check_write(to, n); kcsan_check_write(to, n); + uaccess_buffer_log_read(from, n); } #endif /* _LINUX_INSTRUMENTED_H */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 78c351e35fec..1f978deaa3f8 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1484,6 +1484,10 @@ struct task_struct { struct callback_head l1d_flush_kill; #endif +#ifdef CONFIG_HAVE_ARCH_UACCESS_BUFFER + struct uaccess_buffer_info uaccess_buffer; +#endif + /* * New fields for task_struct should be added above here, so that * they are included in the randomized portion of task_struct. diff --git a/include/linux/uaccess-buffer-log-hooks.h b/include/linux/uaccess-buffer-log-hooks.h new file mode 100644 index 000000000000..bddc84ddce32 --- /dev/null +++ b/include/linux/uaccess-buffer-log-hooks.h @@ -0,0 +1,59 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_UACCESS_BUFFER_LOG_HOOKS_H +#define _LINUX_UACCESS_BUFFER_LOG_HOOKS_H + +#ifdef CONFIG_HAVE_ARCH_UACCESS_BUFFER + +struct uaccess_buffer_info { + /* + * The pointer to pointer to struct uaccess_descriptor. This is the + * value controlled by prctl(PR_SET_UACCESS_DESCRIPTOR_ADDR_ADDR). + */ + struct uaccess_descriptor __user *__user *desc_ptr_ptr; + + /* + * The pointer to struct uaccess_descriptor read at syscall entry time. + */ + struct uaccess_descriptor __user *desc_ptr; + + /* + * A pointer to the kernel's temporary copy of the uaccess log for the + * current syscall. We log to a kernel buffer in order to avoid leaking + * timing information to userspace. + */ + struct uaccess_buffer_entry *kbegin; + + /* + * The position of the next uaccess buffer entry for the current + * syscall. + */ + struct uaccess_buffer_entry *kcur; + + /* + * A pointer to the end of the kernel's uaccess log. + */ + struct uaccess_buffer_entry *kend; + + /* + * The pointer to the userspace uaccess log, as read from the + * struct uaccess_descriptor. + */ + struct uaccess_buffer_entry __user *ubegin; +}; + +void uaccess_buffer_log_read(const void __user *from, unsigned long n); +void uaccess_buffer_log_write(void __user *to, unsigned long n); + +#else + +static inline void uaccess_buffer_log_read(const void __user *from, + unsigned long n) +{ +} +static inline void uaccess_buffer_log_write(void __user *to, unsigned long n) +{ +} + +#endif + +#endif /* _LINUX_UACCESS_BUFFER_LOG_HOOKS_H */ diff --git a/include/linux/uaccess-buffer.h b/include/linux/uaccess-buffer.h new file mode 100644 index 000000000000..14261368d3a9 --- /dev/null +++ b/include/linux/uaccess-buffer.h @@ -0,0 +1,79 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_UACCESS_BUFFER_H +#define _LINUX_UACCESS_BUFFER_H + +#include +#include + +#include + +#ifdef CONFIG_HAVE_ARCH_UACCESS_BUFFER + +static inline bool uaccess_buffer_maybe_blocked(struct task_struct *tsk) +{ + return tsk->uaccess_buffer.desc_ptr_ptr; +} + +void __uaccess_buffer_syscall_entry(void); +static inline void uaccess_buffer_syscall_entry(void) +{ + if (uaccess_buffer_maybe_blocked(current)) + __uaccess_buffer_syscall_entry(); +} + +void __uaccess_buffer_syscall_exit(void); +static inline void uaccess_buffer_syscall_exit(void) +{ + if (uaccess_buffer_maybe_blocked(current)) + __uaccess_buffer_syscall_exit(); +} + +bool __uaccess_buffer_pre_exit_loop(void); +static inline bool uaccess_buffer_pre_exit_loop(void) +{ + if (!uaccess_buffer_maybe_blocked(current)) + return false; + return __uaccess_buffer_pre_exit_loop(); +} + +void __uaccess_buffer_post_exit_loop(void); +static inline void uaccess_buffer_post_exit_loop(bool pending) +{ + if (pending) + __uaccess_buffer_post_exit_loop(); +} + +void uaccess_buffer_cancel_log(struct task_struct *tsk); +int uaccess_buffer_set_descriptor_addr_addr(unsigned long addr); + +#else + +static inline bool uaccess_buffer_maybe_blocked(struct task_struct *tsk) +{ + return false; +} + +static inline void uaccess_buffer_syscall_entry(void) +{ +} +static inline void uaccess_buffer_syscall_exit(void) +{ +} +static inline bool uaccess_buffer_pre_exit_loop(void) +{ + return false; +} +static inline void uaccess_buffer_post_exit_loop(bool pending) +{ +} +static inline void uaccess_buffer_cancel_log(struct task_struct *tsk) +{ +} + +static inline int uaccess_buffer_set_descriptor_addr_addr(unsigned long addr) +{ + return -EINVAL; +} +#endif + +#endif /* _LINUX_UACCESS_BUFFER_H */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index bb73e9a0b24f..74b37469c7b3 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -272,4 +272,7 @@ struct prctl_mm_map { # define PR_SCHED_CORE_SCOPE_THREAD_GROUP 1 # define PR_SCHED_CORE_SCOPE_PROCESS_GROUP 2 +/* Configure uaccess logging feature */ +#define PR_SET_UACCESS_DESCRIPTOR_ADDR_ADDR 63 + #endif /* _LINUX_PRCTL_H */ diff --git a/include/uapi/linux/uaccess-buffer.h b/include/uapi/linux/uaccess-buffer.h new file mode 100644 index 000000000000..619b17dc25c4 --- /dev/null +++ b/include/uapi/linux/uaccess-buffer.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_UACCESS_BUFFER_H +#define _UAPI_LINUX_UACCESS_BUFFER_H + +/* Location of the uaccess log. */ +struct uaccess_descriptor { + /* Address of the uaccess_buffer_entry array. */ + __u64 addr; + /* Size of the uaccess_buffer_entry array in number of elements. */ + __u64 size; +}; + +/* Format of the entries in the uaccess log. */ +struct uaccess_buffer_entry { + /* Address being accessed. */ + __u64 addr; + /* Number of bytes that were accessed. */ + __u64 size; + /* UACCESS_BUFFER_* flags. */ + __u64 flags; +}; + +#define UACCESS_BUFFER_FLAG_WRITE 1 /* access was a write */ + +#endif /* _UAPI_LINUX_UACCESS_BUFFER_H */ diff --git a/kernel/Makefile b/kernel/Makefile index 186c49582f45..d4d9be5146c3 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -114,6 +114,7 @@ obj-$(CONFIG_KCSAN) += kcsan/ obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call.o obj-$(CONFIG_CFI_CLANG) += cfi.o +obj-$(CONFIG_HAVE_ARCH_UACCESS_BUFFER) += uaccess-buffer.o obj-$(CONFIG_PERF_EVENTS) += events/ diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 649f07623df6..167b50177066 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -637,7 +637,11 @@ const struct bpf_func_proto bpf_event_output_data_proto = { BPF_CALL_3(bpf_copy_from_user, void *, dst, u32, size, const void __user *, user_ptr) { - int ret = copy_from_user(dst, user_ptr, size); + /* + * Avoid copy_from_user() here as it may leak information about the BPF + * program to userspace via the uaccess buffer. + */ + int ret = raw_copy_from_user(dst, user_ptr, size); if (unlikely(ret)) { memset(dst, 0, size); diff --git a/kernel/fork.c b/kernel/fork.c index 3244cc56b697..c7abe7e7c7cd 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -96,6 +96,7 @@ #include #include #include +#include #include #include @@ -890,6 +891,8 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) if (memcg_charge_kernel_stack(tsk)) goto free_stack; + uaccess_buffer_cancel_log(tsk); + stack_vm_area = task_stack_vm_area(tsk); err = arch_dup_task_struct(tsk, orig); diff --git a/kernel/signal.c b/kernel/signal.c index a629b11bf3e0..69bf21518bd0 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -45,6 +45,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -1031,7 +1032,8 @@ static void complete_signal(int sig, struct task_struct *p, enum pid_type type) if (sig_fatal(p, sig) && !(signal->flags & SIGNAL_GROUP_EXIT) && !sigismember(&t->real_blocked, sig) && - (sig == SIGKILL || !p->ptrace)) { + (sig == SIGKILL || + !(p->ptrace || uaccess_buffer_maybe_blocked(p)))) { /* * This signal will be fatal to the whole group. */ diff --git a/kernel/sys.c b/kernel/sys.c index 8fdac0d90504..c71a9a9c0f68 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -42,6 +42,7 @@ #include #include #include +#include #include #include @@ -2530,6 +2531,11 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, error = sched_core_share_pid(arg2, arg3, arg4, arg5); break; #endif + case PR_SET_UACCESS_DESCRIPTOR_ADDR_ADDR: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = uaccess_buffer_set_descriptor_addr_addr(arg2); + break; default: error = -EINVAL; break; diff --git a/kernel/uaccess-buffer.c b/kernel/uaccess-buffer.c new file mode 100644 index 000000000000..e1c6d6ab9af8 --- /dev/null +++ b/kernel/uaccess-buffer.c @@ -0,0 +1,125 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Support for uaccess logging via uaccess buffers. + * + * Copyright (C) 2021, Google LLC. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static void uaccess_buffer_log(unsigned long addr, unsigned long size, + unsigned long flags) +{ + struct uaccess_buffer_info *buf = ¤t->uaccess_buffer; + struct uaccess_buffer_entry *entry = buf->kcur; + + if (!entry || unlikely(uaccess_kernel())) + return; + entry->addr = addr; + entry->size = size; + entry->flags = flags; + + ++buf->kcur; + if (buf->kcur == buf->kend) + buf->kcur = 0; +} + +void uaccess_buffer_log_read(const void __user *from, unsigned long n) +{ + uaccess_buffer_log((unsigned long)from, n, 0); +} +EXPORT_SYMBOL(uaccess_buffer_log_read); + +void uaccess_buffer_log_write(void __user *to, unsigned long n) +{ + uaccess_buffer_log((unsigned long)to, n, UACCESS_BUFFER_FLAG_WRITE); +} +EXPORT_SYMBOL(uaccess_buffer_log_write); + +int uaccess_buffer_set_descriptor_addr_addr(unsigned long addr) +{ + current->uaccess_buffer.desc_ptr_ptr = + (struct uaccess_descriptor __user * __user *)addr; + uaccess_buffer_cancel_log(current); + return 0; +} + +bool __uaccess_buffer_pre_exit_loop(void) +{ + struct uaccess_buffer_info *buf = ¤t->uaccess_buffer; + struct uaccess_descriptor __user *desc_ptr; + sigset_t tmp_mask; + + if (get_user(desc_ptr, buf->desc_ptr_ptr) || !desc_ptr) + return false; + + current->real_blocked = current->blocked; + sigfillset(&tmp_mask); + set_current_blocked(&tmp_mask); + return true; +} + +void __uaccess_buffer_post_exit_loop(void) +{ + spin_lock_irq(¤t->sighand->siglock); + current->blocked = current->real_blocked; + recalc_sigpending(); + spin_unlock_irq(¤t->sighand->siglock); +} + +void uaccess_buffer_cancel_log(struct task_struct *tsk) +{ + struct uaccess_buffer_info *buf = &tsk->uaccess_buffer; + + if (buf->kcur) { + buf->kcur = 0; + kfree(buf->kbegin); + } +} + +void __uaccess_buffer_syscall_entry(void) +{ + struct uaccess_buffer_info *buf = ¤t->uaccess_buffer; + struct uaccess_descriptor desc; + + if (get_user(buf->desc_ptr, buf->desc_ptr_ptr) || !buf->desc_ptr || + put_user(0, buf->desc_ptr_ptr) || + copy_from_user(&desc, buf->desc_ptr, sizeof(desc))) + return; + + if (desc.size > 1024) + desc.size = 1024; + + buf->kbegin = kmalloc_array( + desc.size, sizeof(struct uaccess_buffer_entry), GFP_KERNEL); + buf->kcur = buf->kbegin; + buf->kend = buf->kbegin + desc.size; + buf->ubegin = (struct uaccess_buffer_entry __user *)desc.addr; +} + +void __uaccess_buffer_syscall_exit(void) +{ + struct uaccess_buffer_info *buf = ¤t->uaccess_buffer; + u64 num_entries = buf->kcur - buf->kbegin; + struct uaccess_descriptor desc; + + if (!buf->kcur) + return; + + desc.addr = (u64)(buf->ubegin + num_entries); + desc.size = buf->kend - buf->kcur; + buf->kcur = 0; + if (copy_to_user(buf->ubegin, buf->kbegin, + num_entries * sizeof(struct uaccess_buffer_entry)) == 0) + (void)copy_to_user(buf->desc_ptr, &desc, sizeof(desc)); + + kfree(buf->kbegin); +}