[moderation] [fs?] KCSAN: data-race in __set_task_comm / strlen (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 848acc8ffe1b Merge tag 'fsverity-for-linus' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1549e3b9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=98baf51f5cc36dcbe2f7
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [amir...@gmail.com ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d1a0ae21bd78/disk-848acc8f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9be505d18eb6/vmlinux-848acc8f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8ab6a3838bc0/bzImage-848acc8f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+98baf5...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __set_task_comm / strlen

write to 0xffff888104b0ccd8 of 10 bytes by task 8633 on cpu 0:
__set_task_comm+0x78/0x180 fs/exec.c:1099
__do_sys_prctl kernel/sys.c:2608 [inline]
__se_sys_prctl+0xcb3/0x13b0 kernel/sys.c:2534
__x64_sys_prctl+0x67/0x80 kernel/sys.c:2534
x64_sys_call+0x2533/0x3020 arch/x86/include/generated/asm/syscalls_64.h:158
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104b0ccdf of 1 bytes by task 4292 on cpu 1:
strlen+0x19/0x40 lib/string.c:402
__fortify_strlen include/linux/fortify-string.h:218 [inline]
trace_event_get_offsets_sched_stat_runtime include/trace/events/sched.h:560 [inline]
do_trace_event_raw_event_sched_stat_runtime include/trace/events/sched.h:553 [inline]
trace_event_raw_event_sched_stat_runtime+0x59/0x140 include/trace/events/sched.h:553
__do_trace_sched_stat_runtime include/trace/events/sched.h:576 [inline]
trace_sched_stat_runtime include/trace/events/sched.h:576 [inline]
update_se+0x153/0x460 kernel/sched/fair.c:1375
update_curr+0x29/0x210 kernel/sched/fair.c:2001
enqueue_entity kernel/sched/fair.c:6121 [inline]
enqueue_task_fair+0x144/0xab0 kernel/sched/fair.c:7857
enqueue_task kernel/sched/core.c:2184 [inline]
activate_task kernel/sched/core.c:2224 [inline]
ttwu_do_activate+0xa7/0x230 kernel/sched/core.c:3824
ttwu_queue kernel/sched/core.c:4077 [inline]
try_to_wake_up+0x44a/0x6c0 kernel/sched/core.c:4415
ep_autoremove_wake_function+0x2c/0xb0 fs/eventpoll.c:2204
__wake_up_common kernel/sched/wait.c:108 [inline]
__wake_up_common_lock kernel/sched/wait.c:125 [inline]
__wake_up+0x66/0xb0 kernel/sched/wait.c:146
ep_poll_callback+0x448/0x590 fs/eventpoll.c:1564
__wake_up_common kernel/sched/wait.c:108 [inline]
__wake_up_common_lock kernel/sched/wait.c:125 [inline]
__wake_up+0x66/0xb0 kernel/sched/wait.c:146
fsnotify_insert_event+0x206/0x240 fs/notify/notification.c:127
fsnotify_add_event include/linux/fsnotify_backend.h:759 [inline]
inotify_handle_inode_event+0x31d/0x3c0 fs/notify/inotify/inotify_fsnotify.c:126
inotify_ignored_and_remove_idr+0x29/0x60 fs/notify/inotify/inotify_user.c:526
inotify_freeing_mark+0x1d/0x30 fs/notify/inotify/inotify_fsnotify.c:140
fsnotify_free_mark fs/notify/mark.c:659 [inline]
fsnotify_destroy_mark+0x123/0x140 fs/notify/mark.c:668
__do_sys_inotify_rm_watch fs/notify/inotify/inotify_user.c:806 [inline]
__se_sys_inotify_rm_watch+0xe8/0x170 fs/notify/inotify/inotify_user.c:787
__x64_sys_inotify_rm_watch+0x31/0x40 fs/notify/inotify/inotify_user.c:787
x64_sys_call+0xc88/0x3020 arch/x86/include/generated/asm/syscalls_64.h:256
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x63 -> 0x33

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4292 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(lazy)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================


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