[syzbot] [perf?] KCSAN: data-race in event_sched_out / perf_mmap_rb

[syzbot] [perf?] KCSAN: data-race in event_sched_out / perf_mmap_rb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    7c6c4ed80b87 Merge tag 'vfs-7.0-rc8.fixes' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1129b302580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9
dashboard link: https://syzkaller.appspot.com/bug?extid=1f011f617ab8493f3fdd
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/952ebc34a0d7/disk-7c6c4ed8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d3c6b295fa45/vmlinux-7c6c4ed8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6cbdb6b4817a/bzImage-7c6c4ed8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f011f617ab8493f3fdd@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in event_sched_out / perf_mmap_rb

read to 0xffff88810e381fd0 of 8 bytes by task 21833 on cpu 0:
 __perf_update_times kernel/events/core.c:749 [inline]
 perf_event_update_time kernel/events/core.c:762 [inline]
 perf_mmap_rb+0x71d/0x950 kernel/events/core.c:7333
 perf_mmap+0x1d7/0x300 kernel/events/core.c:7460
 vfs_mmap include/linux/fs.h:2070 [inline]
 mmap_file mm/internal.h:167 [inline]
 __mmap_new_file_vma mm/vma.c:2468 [inline]
 __mmap_new_vma mm/vma.c:2532 [inline]
 __mmap_region mm/vma.c:2759 [inline]
 mmap_region+0x195e/0x20c0 mm/vma.c:2844
 do_mmap+0x9b2/0xbd0 mm/mmap.c:559
 vm_mmap_pgoff+0x183/0x2d0 mm/util.c:581
 ksys_mmap_pgoff+0x267/0x310 mm/mmap.c:605
 x64_sys_call+0x14df/0x3020 arch/x86/include/generated/asm/syscalls_64.h:10
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

write to 0xffff88810e381fd0 of 8 bytes by task 21809 on cpu 1:
 __perf_update_times kernel/events/core.c:-1 [inline]
 perf_event_update_time kernel/events/core.c:762 [inline]
 perf_event_set_state kernel/events/core.c:781 [inline]
 event_sched_out+0x4c9/0x760 kernel/events/core.c:2484
 group_sched_out kernel/events/core.c:2508 [inline]
 __pmu_ctx_sched_out+0x3e7/0x530 kernel/events/core.c:3555
 ctx_sched_out+0x279/0x2e0 kernel/events/core.c:3646
 task_ctx_sched_out+0x4d/0x70 kernel/events/core.c:2955
 perf_event_context_sched_out kernel/events/core.c:3853 [inline]
 __perf_event_task_sched_out+0x474/0x710 kernel/events/core.c:3953
 perf_event_task_sched_out include/linux/perf_event.h:1662 [inline]
 prepare_task_switch kernel/sched/core.c:5086 [inline]
 context_switch kernel/sched/core.c:5243 [inline]
 __schedule+0xd3b/0xd40 kernel/sched/core.c:6911
 preempt_schedule_common+0x11/0x30 kernel/sched/core.c:7095
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
 _raw_spin_unlock_irqrestore+0x27/0x30 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:407 [inline]
 __wake_up_common_lock kernel/sched/wait.c:127 [inline]
 __wake_up+0x88/0xb0 kernel/sched/wait.c:146
 audit_log_end+0x1e0/0x250 kernel/audit.c:2804
 audit_seccomp+0xdb/0x100 kernel/auditsc.c:2955
 seccomp_log kernel/seccomp.c:1048 [inline]
 __seccomp_filter+0x8ec/0x1350 kernel/seccomp.c:1344
 __secure_computing+0x81/0x150 kernel/seccomp.c:1404
 syscall_trace_enter include/linux/entry-common.h:112 [inline]
 syscall_enter_from_user_mode_work include/linux/entry-common.h:156 [inline]
 syscall_enter_from_user_mode include/linux/entry-common.h:187 [inline]
 do_syscall_64+0xd3/0x370 arch/x86/entry/syscall_64.c:90
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000003d41894 -> 0x0000000003d477ec

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 21809 Comm: syz.0.5496 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup