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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fa5c82f4d2bb slab.h: disable completely broken overflow ha..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14b4a55a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ced7763744c4a3f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3dc6e2ddbbbe238ab883
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
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/a7b7ffe359f8/disk-fa5c82f4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/11e162e0b3a6/vmlinux-fa5c82f4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cf76fb216354/bzImage-fa5c82f4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3dc6e2...@syzkaller.appspotmail.com

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

write to 0xffff8881052d1b20 of 4 bytes by task 13256 on cpu 1:
inode_set_ctime_to_ts fs/inode.c:2779 [inline]
inode_set_ctime_current+0x256/0x960 fs/inode.c:2842
shmem_xattr_handler_set+0x1ac/0x220 mm/shmem.c:4355
__vfs_setxattr+0x2e6/0x310 fs/xattr.c:200
__vfs_setxattr_noperm+0xe8/0x410 fs/xattr.c:234
__vfs_setxattr_locked+0x105/0x220 fs/xattr.c:295
vfs_setxattr+0x12c/0x2a0 fs/xattr.c:321
do_setxattr fs/xattr.c:636 [inline]
filename_setxattr+0x1c4/0x410 fs/xattr.c:664
path_setxattrat+0x2be/0x310 fs/xattr.c:708
__do_sys_lsetxattr fs/xattr.c:749 [inline]
__se_sys_lsetxattr fs/xattr.c:745 [inline]
__x64_sys_lsetxattr+0x71/0x90 fs/xattr.c:745
x64_sys_call+0x1300/0x3020 arch/x86/include/generated/asm/syscalls_64.h:190
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881052d1b20 of 4 bytes by task 3304 on cpu 0:
inode_get_ctime_nsec include/linux/fs.h:1689 [inline]
inode_get_ctime include/linux/fs.h:1695 [inline]
generic_fillattr+0x1d1/0x340 fs/stat.c:101
shmem_getattr+0x181/0x200 mm/shmem.c:1302
vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
vfs_getattr+0x48/0x60 fs/stat.c:262
vfs_statx_path+0x28/0x140 fs/stat.c:299
vfs_statx+0xc4/0x170 fs/stat.c:356
vfs_fstatat+0x118/0x170 fs/stat.c:373
__do_sys_newfstatat fs/stat.c:538 [inline]
__se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x318f95a9 -> 0x0efd7cb1

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3304 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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