[moderation] [fs?] KCSAN: data-race in atime_needs_update / inode_set_ctime_to_ts (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cf1ea8854e4f Merge tag 'mmc-v6.18-rc1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14d975e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bafeb347352dd60e
dashboard link: https://syzkaller.appspot.com/bug?extid=bda02411d7835c0eb5bc
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/7252fbf4224f/disk-cf1ea885.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/23f17dbd0e20/vmlinux-cf1ea885.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0edb5d25fd04/bzImage-cf1ea885.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bda024...@syzkaller.appspotmail.com

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

write to 0xffff88811e1d5b20 of 4 bytes by task 3778 on cpu 0:
inode_set_ctime_to_ts+0x84/0x170 fs/inode.c:2715
inode_set_ctime_current+0x1d6/0x770 fs/inode.c:2778
shmem_xattr_handler_set+0x1ac/0x220 mm/shmem.c:4336
__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+0x287b/0x3000 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 0xffff88811e1d5b20 of 4 bytes by task 3301 on cpu 1:
inode_get_ctime_nsec include/linux/fs.h:1869 [inline]
inode_get_ctime include/linux/fs.h:1875 [inline]
relatime_need_update fs/inode.c:2018 [inline]
atime_needs_update+0x333/0x3e0 fs/inode.c:2158
touch_atime+0x4a/0x340 fs/inode.c:2173
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+0x28de/0x3000 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: 0x22fee768 -> 0x24301468

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3301 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
==================================================================


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