[moderation] [fs?] [mm?] KCSAN: data-race in __set_task_comm / strlen

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9dd1835ecda5 Merge tag 'dma-mapping-6.17-2025-09-09' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=138e4d62580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=cfff6bf0b01901fca878
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 ke...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org linu...@kvack.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/bed60878f1bb/disk-9dd1835e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7a737ddc0fed/vmlinux-9dd1835e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/39c2c269c318/bzImage-9dd1835e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cfff6b...@syzkaller.appspotmail.com

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

write to 0xffff8881951c17f8 of 8 bytes by task 27425 on cpu 0:
__set_task_comm+0x4d/0x140 fs/exec.c:1088
begin_new_exec+0xeb3/0x1160 fs/exec.c:1246
load_elf_binary+0x62b/0x1a20 fs/binfmt_elf.c:995
search_binary_handler fs/exec.c:1670 [inline]
exec_binprm fs/exec.c:1702 [inline]
bprm_execve+0x477/0x970 fs/exec.c:1754
kernel_execve+0x617/0x660 fs/exec.c:1920
call_usermodehelper_exec_async+0x197/0x250 kernel/umh.c:109
ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881951c17ff of 1 bytes by task 27384 on cpu 1:
strlen+0x19/0x40 lib/string.c:420
__fortify_strlen include/linux/fortify-string.h:268 [inline]
trace_event_get_offsets_sched_stat_runtime include/trace/events/sched.h:553 [inline]
do_perf_trace_sched_stat_runtime include/trace/events/sched.h:553 [inline]
perf_trace_sched_stat_runtime+0x3c/0x150 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+0x129/0x140 kernel/sched/fair.c:1175
update_curr+0x2c/0x1b0 kernel/sched/fair.c:1223
enqueue_entity kernel/sched/fair.c:5253 [inline]
enqueue_task_fair+0x146/0x980 kernel/sched/fair.c:6876
enqueue_task kernel/sched/core.c:2090 [inline]
activate_task+0x59/0xb0 kernel/sched/core.c:2132
ttwu_do_activate+0x69/0x210 kernel/sched/core.c:3741
ttwu_queue kernel/sched/core.c:4004 [inline]
try_to_wake_up+0x37f/0x630 kernel/sched/core.c:4328
wake_up_process kernel/sched/core.c:4459 [inline]
wake_up_q+0x48/0x80 kernel/sched/core.c:1084
futex_wake+0x2f1/0x360 kernel/futex/waitwake.c:198
do_futex+0x323/0x380 kernel/futex/syscalls.c:107
__do_sys_futex kernel/futex/syscalls.c:179 [inline]
__se_sys_futex+0x2ed/0x360 kernel/futex/syscalls.c:160
__x64_sys_futex+0x78/0x90 kernel/futex/syscalls.c:160
x64_sys_call+0x2e39/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:203
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: 0x2f -> 0x65

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 27384 Comm: syz.1.7846 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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