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Message-ID: <2024110928-CVE-2024-50228-7a2a@gregkh> Date: Sat, 9 Nov 2024 11:15:36 +0100 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Subject: CVE-2024-50228: mm: shmem: fix data-race in shmem_getattr() Description =========== In the Linux kernel, the following vulnerability has been resolved: mm: shmem: fix data-race in shmem_getattr() 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. The Linux kernel CVE team has assigned CVE-2024-50228 to this issue. Affected and fixed versions =========================== Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 4.19.323 with commit 9fb9703cd43e Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 5.4.285 with commit 7cc30ada8432 Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 5.10.229 with commit bda1a99a0dd6 Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 5.15.171 with commit 3d9528484480 Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 6.1.116 with commit 82cae1e30bd9 Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 6.6.60 with commit edd1f9050506 Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 6.11.7 with commit ffd56612566b Issue introduced in 4.3 with commit 44a30220bc0a and fixed in 6.12-rc6 with commit d949d1d14fa2 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2024-50228 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: mm/shmem.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/9fb9703cd43ee20a6de8ccdef991677b7274cec0 https://git.kernel.org/stable/c/7cc30ada84323be19395094d567579536e0d187e https://git.kernel.org/stable/c/bda1a99a0dd644f31a87d636ac624eeb975cb65a https://git.kernel.org/stable/c/3d9528484480e8f4979b3a347930ed383be99f89 https://git.kernel.org/stable/c/82cae1e30bd940253593c2d4f16d88343d1358f4 https://git.kernel.org/stable/c/edd1f905050686fdc4cfe233d818469fdf7d5ff8 https://git.kernel.org/stable/c/ffd56612566bc23877c8f45def2801f3324a222a https://git.kernel.org/stable/c/d949d1d14fa281ace388b1de978e8f2cd52875cf
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