From mboxrd@z Thu Jan 1 00:00:00 1970 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 E99571DF98C; Wed, 6 Nov 2024 12:23:49 +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=1730895830; cv=none; b=R8qC6tdzU9HdHLDn0R7F7GNyx5g8EmuOiZGRxb3Uf9ezTqKEkFD+22+sdE0JTdHsw2jxcdoMzOqoM3AdVeyKheEucD7BH1a3ybUKCEwnruLS+pyLoIW0C6+XqQs2E3io02GCh5qoPlAvkhlMpvd5MPuOC7YQaqnLicFpvOc05AY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730895830; c=relaxed/simple; bh=bBXNyyDsaCk77zODsNcMvA1aDZs1SI4+7lwneiXm6n0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CVKy8YNEEsqI+r/XPTdZYoXFS1bfzDiydh4WtN0U0F09rXtRQMdNNzWA4GGlKitQMgZ2EmkGcuwKMh74cAmPYABeXThApYa8Yz974/7xkqZAw4GJj9ygzBK1VA8uhsZXUFyhE/CwP28zJUhufeaTEkxW+BRWMfVx0VTEi9ZB49A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lrtK6RNh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="lrtK6RNh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 70F31C4CECD; Wed, 6 Nov 2024 12:23:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1730895829; bh=bBXNyyDsaCk77zODsNcMvA1aDZs1SI4+7lwneiXm6n0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lrtK6RNh/23qjy4Pg+GkwMSIZ3ylxZwtkBKzM1h61lH+QSvZR+npU+URRLPJwqWTy JjYbhutY/HOt9CS3dK+CW52KxWbal2gjBozrTfCrrGkC3VbBQiuGZEkp9mXVsFarmk KbuxtO04XPQzwPmr1/L9K3c9dZekeK8v9E4d3N10= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jeongjun Park , syzbot , Hugh Dickins , Yu Zhao , Andrew Morton Subject: [PATCH 4.19 349/350] mm: shmem: fix data-race in shmem_getattr() Date: Wed, 6 Nov 2024 13:04:37 +0100 Message-ID: <20241106120329.300030478@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241106120320.865793091@linuxfoundation.org> References: <20241106120320.865793091@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jeongjun Park commit d949d1d14fa281ace388b1de978e8f2cd52875cf upstream. I got the following KCSAN report during syzbot testing: ================================================================== BUG: KCSAN: data-race in generic_fillattr / inode_set_ctime_current write to 0xffff888102eb3260 of 4 bytes by task 6565 on cpu 1: inode_set_ctime_to_ts include/linux/fs.h:1638 [inline] inode_set_ctime_current+0x169/0x1d0 fs/inode.c:2626 shmem_mknod+0x117/0x180 mm/shmem.c:3443 shmem_create+0x34/0x40 mm/shmem.c:3497 lookup_open fs/namei.c:3578 [inline] open_last_lookups fs/namei.c:3647 [inline] path_openat+0xdbc/0x1f00 fs/namei.c:3883 do_filp_open+0xf7/0x200 fs/namei.c:3913 do_sys_openat2+0xab/0x120 fs/open.c:1416 do_sys_open fs/open.c:1431 [inline] __do_sys_openat fs/open.c:1447 [inline] __se_sys_openat fs/open.c:1442 [inline] __x64_sys_openat+0xf3/0x120 fs/open.c:1442 x64_sys_call+0x1025/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:258 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x76/0x7e read to 0xffff888102eb3260 of 4 bytes by task 3498 on cpu 0: inode_get_ctime_nsec include/linux/fs.h:1623 [inline] inode_get_ctime include/linux/fs.h:1629 [inline] generic_fillattr+0x1dd/0x2f0 fs/stat.c:62 shmem_getattr+0x17b/0x200 mm/shmem.c:1157 vfs_getattr_nosec fs/stat.c:166 [inline] vfs_getattr+0x19b/0x1e0 fs/stat.c:207 vfs_statx_path fs/stat.c:251 [inline] vfs_statx+0x134/0x2f0 fs/stat.c:315 vfs_fstatat+0xec/0x110 fs/stat.c:341 __do_sys_newfstatat fs/stat.c:505 [inline] __se_sys_newfstatat+0x58/0x260 fs/stat.c:499 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:499 x64_sys_call+0x141f/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:263 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x54/0x120 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x76/0x7e value changed: 0x2755ae53 -> 0x27ee44d3 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 3498 Comm: udevd Not tainted 6.11.0-rc6-syzkaller-00326-gd1f2d51b711a-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 ================================================================== When calling generic_fillattr(), if you don't hold read lock, data-race will occur in inode member variables, which can cause unexpected behavior. Since there is no special protection when shmem_getattr() calls generic_fillattr(), data-race occurs by functions such as shmem_unlink() or shmem_mknod(). This can cause unexpected results, so commenting it out is not enough. Therefore, when calling generic_fillattr() from shmem_getattr(), it is appropriate to protect the inode using inode_lock_shared() and inode_unlock_shared() to prevent data-race. Link: https://lkml.kernel.org/r/20240909123558.70229-1-aha310510@gmail.com Fixes: 44a30220bc0a ("shmem: recalculate file inode when fstat") Signed-off-by: Jeongjun Park Reported-by: syzbot Cc: Hugh Dickins Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/shmem.c | 2 ++ 1 file changed, 2 insertions(+) --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1014,7 +1014,9 @@ static int shmem_getattr(const struct pa shmem_recalc_inode(inode); spin_unlock_irq(&info->lock); } + inode_lock_shared(inode); generic_fillattr(inode, stat); + inode_unlock_shared(inode); if (is_huge_enabled(sb_info)) stat->blksize = HPAGE_PMD_SIZE;