syzbot


KCSAN: data-race in memcpy_and_pad / perf_remove_from_owner

Status: moderation: reported on 2026/03/21 08:34
Subsystems: perf
[Documentation on labels]
Reported-by: syzbot+eacca7447d304884ae62@syzkaller.appspotmail.com
First crash: 4d11h, last: 4d11h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
22a4b5a6-9a45-4b2f-9cb7-abfaa03114f3 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in memcpy_and_pad / perf_remove_from_owner 2026/03/21 08:34 2026/03/21 08:34 2026/03/21 08:51 f84caa2f84dea47b51a188e8d6267f295e89bbcb

Sample crash report:
==================================================================
BUG: KCSAN: data-race in memcpy_and_pad / perf_remove_from_owner

write to 0xffff888104c28a10 of 8 bytes by task 17291 on cpu 0:
 __list_del include/linux/list.h:203 [inline]
 __list_del_entry include/linux/list.h:226 [inline]
 list_del_init include/linux/list.h:295 [inline]
 perf_remove_from_owner+0xe6/0x1f0 kernel/events/core.c:5897
 perf_event_release_kernel+0x6a/0x510 kernel/events/core.c:5941
 perf_release+0x1f/0x30 kernel/events/core.c:6033
 __fput+0x29b/0x650 fs/file_table.c:469
 ____fput+0x1c/0x30 fs/file_table.c:497
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0x1f4/0x6f0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104c28000 of 3328 bytes by task 17292 on cpu 1:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1008
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:108
 dup_task_struct+0x6e/0x950 kernel/fork.c:920
 copy_process+0x37e/0x20b0 kernel/fork.c:2050
 create_io_thread+0x8f/0xc0 kernel/fork.c:2601
 create_worker_cont+0x5f/0x380 io_uring/io-wq.c:852
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 get_signal+0xe0e/0xf60 kernel/signal.c:2807
 arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 17292 Comm: syz.3.2996 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/21 08:34 upstream 42bddab0563f 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in memcpy_and_pad / perf_remove_from_owner
* Struck through repros no longer work on HEAD.