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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7839932417dd Merge tag 'sched_ext-for-6.19-rc3-fixes' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10d8bbb4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=e55f5a246004ff41d932
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/1215db8aa742/disk-78399324.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ec810c593e84/vmlinux-78399324.xz
kernel image: https://storage.googleapis.com/syzbot-assets/39a26f9ca191/bzImage-78399324.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e55f5a...@syzkaller.appspotmail.com

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

write to 0xffff88811b0f7b18 of 4 bytes by task 7903 on cpu 0:
inode_set_ctime_to_ts+0x84/0x170 fs/inode.c:2745
inode_set_ctime_current+0x1cd/0x760 fs/inode.c:2808
inode_update_timestamps+0x84/0x270 fs/inode.c:2109
generic_update_time fs/inode.c:2148 [inline]
inode_update_time fs/inode.c:2168 [inline]
file_update_time_flags+0x26c/0x310 fs/inode.c:2395
file_update_time+0x17/0x20 fs/inode.c:2416
blkdev_write_iter+0x32e/0x4b0 block/fops.c:786
iter_file_splice_write+0x66b/0xa20 fs/splice.c:738
do_splice_from fs/splice.c:938 [inline]
direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
splice_direct_to_actor+0x312/0x680 fs/splice.c:1105
do_splice_direct_actor fs/splice.c:1204 [inline]
do_splice_direct+0xda/0x150 fs/splice.c:1230
do_sendfile+0x380/0x650 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64 fs/read_write.c:1417 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
x64_sys_call+0x2db1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b0f7b18 of 4 bytes by task 3305 on cpu 1:
inode_get_ctime_nsec include/linux/fs.h:1688 [inline]
inode_get_ctime include/linux/fs.h:1694 [inline]
relatime_need_update fs/inode.c:2068 [inline]
atime_needs_update+0x333/0x3e0 fs/inode.c:2208
touch_atime+0x4a/0x340 fs/inode.c:2223
file_accessed include/linux/fs.h:2254 [inline]
filemap_read+0x960/0xa00 mm/filemap.c:2872
blkdev_read_iter+0x22d/0x2e0 block/fops.c:856
new_sync_read fs/read_write.c:491 [inline]
vfs_read+0x64c/0x770 fs/read_write.c:572
ksys_read+0xda/0x1a0 fs/read_write.c:715
__do_sys_read fs/read_write.c:724 [inline]
__se_sys_read fs/read_write.c:722 [inline]
__x64_sys_read+0x40/0x50 fs/read_write.c:722
x64_sys_call+0x2889/0x3000 arch/x86/include/generated/asm/syscalls_64.h:1
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x35ad61f6 -> 0x370cb5e8

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3305 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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