From patchwork Tue Apr 12 19:30:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12811148 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E02CC433F5 for ; Tue, 12 Apr 2022 19:30:31 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id BC1F86B0072; Tue, 12 Apr 2022 15:30:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B71DA6B0073; Tue, 12 Apr 2022 15:30:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A13FE6B0074; Tue, 12 Apr 2022 15:30:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.26]) by kanga.kvack.org (Postfix) with ESMTP id 909156B0072 for ; Tue, 12 Apr 2022 15:30:30 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 61936208D3 for ; Tue, 12 Apr 2022 19:30:30 +0000 (UTC) X-FDA: 79349218620.06.D8A768A Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) by imf05.hostedemail.com (Postfix) with ESMTP id C7FDF100002 for ; Tue, 12 Apr 2022 19:30:29 +0000 (UTC) Received: by mail-yb1-f202.google.com with SMTP id t190-20020a25c3c7000000b006410799ab3dso9927825ybf.21 for ; Tue, 12 Apr 2022 12:30:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=K76R4rEKkjlaPYFhf6H+Upxgkh3tctSxqt3BRQjJcbo=; b=Q9escs89P1qVB1aHoqL3Y/Z6DCzgQIrqEo+YakS5+JxzhC2XUetaEg8TKaD+KTn9cj H4QVS+DV4b05ZpcDI+5H4YPk6hQn6xQ1WHt2wsMhR5RI0xLRWHIJrF58Umz3MeIIoEiX s81JKOwLlmFfieM9vTYhv3omAvshkMOwubfRBCiDkZCUgLny7Dr2iq74zgaO0ZL6mG0+ ImAgF9StO6Xtz1+DOlZ8rUtfmd+MD7pY3O/n+In5S9/Szq/LE0syrT69WqBIrxuAyyEd W/8Ayj9N9l3IfCIXdAXx8PviEfK8hO6TGe0IctMhomNWHAuEvQWGIEsy/PLqR4XpSbqA NdFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=K76R4rEKkjlaPYFhf6H+Upxgkh3tctSxqt3BRQjJcbo=; b=dMFkrhxpqFwVtxeg7iMnn5D/oIwlwwp+WNGkFUanE/mlBJV9fPyxb56ObGDhXGImeP mCwbOZ9tPt8pHSSOGWE/uFsVMZEKHqsy5zx2P/pytaLEC9TocGpteV6XCNeVf74LUFbu rNiiJaJAh+M9E+yhX+pa6aZrSFbBhnbmqgXR20soO5SikxdwmUY1ttoSiUb7OLAPONti t4kjb7hpWNbuPbInVyL0rQqql4KLlD/aksUAdLfMPV1GyWAa3Dn4hGZ9eiO60WHenj2J UTgZFRaGVwesIjoNHOkjvBDtGZtNaEHWBiPJph5SNQkCNrHx4jGMLxPPHavVtG5QEdXg YI+A== X-Gm-Message-State: AOAM53366En1mDFsO7zS71ra8ZDNl3wKLkEQzQ4Q4ovlAqY6FOJ963jN YinB5kLH5JeiKvcs/RTe7xCzO0gfRxUX8gGVsM01 X-Google-Smtp-Source: ABdhPJxL2/UJhRa89Yqrl604aDYp3JBDGDWsKHj9D5kcRd67oGDSCKYQlpp+R9aCVLif/HHhGZwTyrHkJ08f79jImdw+ X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:8927:f9ed:8b14:ddae]) (user=axelrasmussen job=sendgmr) by 2002:a25:ca8f:0:b0:641:2bff:281f with SMTP id a137-20020a25ca8f000000b006412bff281fmr10710225ybg.159.1649791828989; Tue, 12 Apr 2022 12:30:28 -0700 (PDT) Date: Tue, 12 Apr 2022 12:30:23 -0700 Message-Id: <20220412193023.279320-1-axelrasmussen@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.35.1.1178.g4f1659d476-goog Subject: [PATCH v2] mm/secretmem: fix panic when growing a memfd_secret From: Axel Rasmussen To: Andrew Morton , Mike Rapoport Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Axel Rasmussen , stable@vger.kernel.org X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C7FDF100002 X-Stat-Signature: rtso6ir3fsk8c3apiw39jh4rdngeqdn1 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Q9escs89; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf05.hostedemail.com: domain of 3VNNVYg0KCGsJgNUaJbVdbbNWPXXPUN.LXVURWdg-VVTeJLT.XaP@flex--axelrasmussen.bounces.google.com designates 209.85.219.202 as permitted sender) smtp.mailfrom=3VNNVYg0KCGsJgNUaJbVdbbNWPXXPUN.LXVURWdg-VVTeJLT.XaP@flex--axelrasmussen.bounces.google.com X-Rspam-User: X-HE-Tag: 1649791829-375713 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: When one tries to grow an existing memfd_secret with ftruncate, one gets a panic [1]. For example, doing the following reliably induces the panic: fd = memfd_secret(); ftruncate(fd, 10); ptr = mmap(NULL, 10, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); strcpy(ptr, "123456789"); munmap(ptr, 10); ftruncate(fd, 20); The basic reason for this is, when we grow with ftruncate, we call down into simple_setattr, and then truncate_inode_pages_range, and eventually we try to zero part of the memory. The normal truncation code does this via the direct map (i.e., it calls page_address() and hands that to memset()). For memfd_secret though, we specifically don't map our pages via the direct map (i.e. we call set_direct_map_invalid_noflush() on every fault). So the address returned by page_address() isn't useful, and when we try to memset() with it we panic. This patch avoids the panic by implementing a custom setattr for memfd_secret, which detects resizes specifically (setting the size for the first time works just fine, since there are no existing pages to try to zero), and rejects them with EINVAL. One could argue growing should be supported, but I think that will require a significantly more lengthy change. So, I propose a minimal fix for the benefit of stable kernels, and then perhaps to extend memfd_secret to support growing in a separate patch. v2: Make secretmem_iops static to fix build warning, and return EINVAL. [1]: [ 774.320433] BUG: unable to handle page fault for address: ffffa0a889277028 [ 774.322297] #PF: supervisor write access in kernel mode [ 774.323306] #PF: error_code(0x0002) - not-present page [ 774.324296] PGD afa01067 P4D afa01067 PUD 83f909067 PMD 83f8bf067 PTE 800ffffef6d88060 [ 774.325841] Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI [ 774.326934] CPU: 0 PID: 281 Comm: repro Not tainted 5.17.0-dbg-DEV #1 [ 774.328074] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 [ 774.329732] RIP: 0010:memset_erms+0x9/0x10 [ 774.330474] Code: c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 aa 4c 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01 [ 774.333543] RSP: 0018:ffffb932c09afbf0 EFLAGS: 00010246 [ 774.334404] RAX: 0000000000000000 RBX: ffffda63c4249dc0 RCX: 0000000000000fd8 [ 774.335545] RDX: 0000000000000fd8 RSI: 0000000000000000 RDI: ffffa0a889277028 [ 774.336685] RBP: ffffb932c09afc00 R08: 0000000000001000 R09: ffffa0a889277028 [ 774.337929] R10: 0000000000020023 R11: 0000000000000000 R12: ffffda63c4249dc0 [ 774.339236] R13: ffffa0a890d70d98 R14: 0000000000000028 R15: 0000000000000fd8 [ 774.340356] FS: 00007f7294899580(0000) GS:ffffa0af9bc00000(0000) knlGS:0000000000000000 [ 774.341635] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 774.342535] CR2: ffffa0a889277028 CR3: 0000000107ef6006 CR4: 0000000000370ef0 [ 774.343651] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 774.344780] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 774.345938] Call Trace: [ 774.346334] [ 774.346671] ? zero_user_segments+0x82/0x190 [ 774.347346] truncate_inode_partial_folio+0xd4/0x2a0 [ 774.348128] truncate_inode_pages_range+0x380/0x830 [ 774.348904] truncate_setsize+0x63/0x80 [ 774.349530] simple_setattr+0x37/0x60 [ 774.350102] notify_change+0x3d8/0x4d0 [ 774.350681] do_sys_ftruncate+0x162/0x1d0 [ 774.351302] __x64_sys_ftruncate+0x1c/0x20 [ 774.351936] do_syscall_64+0x44/0xa0 [ 774.352486] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 774.353284] RIP: 0033:0x7f72947c392b [ 774.354001] Code: 77 05 c3 0f 1f 40 00 48 8b 15 41 85 0c 00 f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 4d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 11 85 0c 00 f7 d8 [ 774.357938] RSP: 002b:00007ffcad62a1a8 EFLAGS: 00000202 ORIG_RAX: 000000000000004d [ 774.359116] RAX: ffffffffffffffda RBX: 000055f47662b440 RCX: 00007f72947c392b [ 774.360186] RDX: 0000000000000028 RSI: 0000000000000028 RDI: 0000000000000003 [ 774.361246] RBP: 00007ffcad62a1c0 R08: 0000000000000003 R09: 0000000000000000 [ 774.362324] R10: 00007f72946dc230 R11: 0000000000000202 R12: 000055f47662b0e0 [ 774.363393] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 774.364470] [ 774.364807] Modules linked in: xhci_pci xhci_hcd virtio_net net_failover failover virtio_blk virtio_balloon uhci_hcd ohci_pci ohci_hcd evdev ehci_pci ehci_hcd 9pnet_virtio 9p netfs 9pnet [ 774.367325] CR2: ffffa0a889277028 [ 774.367838] ---[ end trace 0000000000000000 ]--- [ 774.368543] RIP: 0010:memset_erms+0x9/0x10 [ 774.369187] Code: c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 aa 4c 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01 [ 774.372282] RSP: 0018:ffffb932c09afbf0 EFLAGS: 00010246 [ 774.373372] RAX: 0000000000000000 RBX: ffffda63c4249dc0 RCX: 0000000000000fd8 [ 774.374814] RDX: 0000000000000fd8 RSI: 0000000000000000 RDI: ffffa0a889277028 [ 774.376248] RBP: ffffb932c09afc00 R08: 0000000000001000 R09: ffffa0a889277028 [ 774.377687] R10: 0000000000020023 R11: 0000000000000000 R12: ffffda63c4249dc0 [ 774.379135] R13: ffffa0a890d70d98 R14: 0000000000000028 R15: 0000000000000fd8 [ 774.380550] FS: 00007f7294899580(0000) GS:ffffa0af9bc00000(0000) knlGS:0000000000000000 [ 774.382177] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 774.383329] CR2: ffffa0a889277028 CR3: 0000000107ef6006 CR4: 0000000000370ef0 [ 774.384763] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 774.386229] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 774.387664] Kernel panic - not syncing: Fatal exception [ 774.388863] Kernel Offset: 0x8000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 774.391014] ---[ end Kernel panic - not syncing: Fatal exception ]--- Signed-off-by: Axel Rasmussen Cc: stable@vger.kernel.org --- mm/secretmem.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/mm/secretmem.c b/mm/secretmem.c index 098638d3b8a4..3b3cf2892b6a 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c @@ -158,6 +158,22 @@ const struct address_space_operations secretmem_aops = { .isolate_page = secretmem_isolate_page, }; +static int secretmem_setattr(struct user_namespace *mnt_userns, + struct dentry *dentry, struct iattr *iattr) +{ + struct inode *inode = d_inode(dentry); + unsigned int ia_valid = iattr->ia_valid; + + if ((ia_valid & ATTR_SIZE) && inode->i_size) + return -EINVAL; + + return simple_setattr(mnt_userns, dentry, iattr); +} + +static const struct inode_operations secretmem_iops = { + .setattr = secretmem_setattr, +}; + static struct vfsmount *secretmem_mnt; static struct file *secretmem_file_create(unsigned long flags) @@ -177,6 +193,7 @@ static struct file *secretmem_file_create(unsigned long flags) mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); mapping_set_unevictable(inode->i_mapping); + inode->i_op = &secretmem_iops; inode->i_mapping->a_ops = &secretmem_aops; /* pretend we are a normal file with zero size */