[moderation] [fs?] KCSAN: data-race in atime_needs_update / inode_set_ctime_to_ts

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5b032cac6225 Merge tag 'ubifs-for-linus-6.16-rc1' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15bcf282580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b473f115729830aa
dashboard link: https://syzkaller.appspot.com/bug?extid=4fb489b18accb3c616c7
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
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/cab37c5943c0/disk-5b032cac.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/535be9c58f0a/vmlinux-5b032cac.xz
kernel image: https://storage.googleapis.com/syzbot-assets/156388789060/bzImage-5b032cac.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4fb489...@syzkaller.appspotmail.com

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

write to 0xffff888104251b10 of 8 bytes by task 3299 on cpu 1:
inode_set_ctime_to_ts+0x72/0x170 fs/inode.c:2667
inode_set_ctime_current+0x1d6/0x770 fs/inode.c:2731
shmem_xattr_handler_set+0x1ac/0x220 mm/shmem.c:4335
__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+0x1e36/0x2fb0 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 0xffff888104251b10 of 8 bytes by task 11633 on cpu 0:
inode_get_ctime_sec include/linux/fs.h:1741 [inline]
inode_get_ctime include/linux/fs.h:1751 [inline]
relatime_need_update fs/inode.c:1977 [inline]
atime_needs_update+0x2ef/0x3e0 fs/inode.c:2117
touch_atime+0x4a/0x340 fs/inode.c:2132
do_readlinkat+0x134/0x320 fs/stat.c:589
__do_sys_readlink fs/stat.c:613 [inline]
__se_sys_readlink fs/stat.c:610 [inline]
__x64_sys_readlink+0x47/0x60 fs/stat.c:610
x64_sys_call+0x2cf3/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:90
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: 0x0000000068447b39 -> 0x0000000068447b3a

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11633 Comm: udevd Tainted: G W 6.15.0-syzkaller-13659-g5b032cac6225 #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.