[moderation] [fs?] KCSAN: data-race in generic_fillattr / inode_set_ctime_to_ts (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cd89d487374c Merge tag '6.17-rc6-smb3-client-fixes' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13bfbe42580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=ccb40cebc41c3a03c891
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fc2828b7b602/disk-cd89d487.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f8144cce2d27/vmlinux-cd89d487.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2dfeac647538/bzImage-cd89d487.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ccb40c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in generic_fillattr / inode_set_ctime_to_ts

write to 0xffff888119d060f0 of 4 bytes by task 3300 on cpu 0:
inode_set_ctime_to_ts+0x84/0x170 fs/inode.c:2667
inode_set_ctime_current+0x1d6/0x770 fs/inode.c:2730
shmem_xattr_handler_set+0x1ac/0x220 mm/shmem.c:4400
__vfs_setxattr+0x2e6/0x310 fs/xattr.c:200
__vfs_setxattr_noperm+0xe8/0x410 fs/xattr.c:234
__vfs_setxattr_locked+0x1af/0x1d0 fs/xattr.c:295
vfs_setxattr+0x132/0x270 fs/xattr.c:321
do_setxattr fs/xattr.c:636 [inline]
filename_setxattr+0x1ad/0x400 fs/xattr.c:665
path_setxattrat+0x2c9/0x310 fs/xattr.c:713
__do_sys_lsetxattr fs/xattr.c:754 [inline]
__se_sys_lsetxattr fs/xattr.c:750 [inline]
__x64_sys_lsetxattr+0x71/0x90 fs/xattr.c:750
x64_sys_call+0x2877/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:190
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888119d060f0 of 4 bytes by task 3298 on cpu 1:
inode_get_ctime_nsec include/linux/fs.h:1752 [inline]
inode_get_ctime include/linux/fs.h:1758 [inline]
generic_fillattr+0x1d1/0x340 fs/stat.c:101
shmem_getattr+0x181/0x200 mm/shmem.c:1294
vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
vfs_getattr fs/stat.c:262 [inline]
vfs_statx_path fs/stat.c:299 [inline]
vfs_statx+0x113/0x390 fs/stat.c:356
vfs_fstatat+0x115/0x170 fs/stat.c:375
__do_sys_newfstatat fs/stat.c:542 [inline]
__se_sys_newfstatat+0x55/0x260 fs/stat.c:536
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:536
x64_sys_call+0x135a/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x20605458 -> 0x22c2ae59

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3298 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================


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