linux-kernel - [syzbot] [perf?] KCSAN: data-race in perf_event_set_state / perf_mmap

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Message-ID: <69859a00.a00a0220.34fa92.0028.GAE@google.com>
Date: Thu, 05 Feb 2026 23:36:32 -0800
From: syzbot <syzbot+5334e6bdc43f6d1dcb7d@...kaller.appspotmail.com>
To: acme@...nel.org, adrian.hunter@...el.com, 
	alexander.shishkin@...ux.intel.com, irogers@...gle.com, 
	james.clark@...aro.org, jolsa@...nel.org, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, mark.rutland@....com, mingo@...hat.com, 
	namhyung@...nel.org, peterz@...radead.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [perf?] KCSAN: data-race in perf_event_set_state / perf_mmap_rb

Hello,

syzbot found the following issue on:

HEAD commit:    c537e12daeec Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1133a5fc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c160236e1ef1e401
dashboard link: https://syzkaller.appspot.com/bug?extid=5334e6bdc43f6d1dcb7d
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/036ac5d12a14/disk-c537e12d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/07ddd15f46f8/vmlinux-c537e12d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7866e67b7a58/bzImage-c537e12d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5334e6bdc43f6d1dcb7d@...kaller.appspotmail.com

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

write to 0xffff88812279f1a0 of 8 bytes by task 12011 on cpu 1:
 perf_event_update_time kernel/events/core.c:737 [inline]
 perf_mmap_rb+0x71c/0x910 kernel/events/core.c:7037
 perf_mmap+0x1ce/0x2f0 kernel/events/core.c:7164
 vfs_mmap include/linux/fs.h:2053 [inline]
 mmap_file mm/internal.h:167 [inline]
 __mmap_new_file_vma mm/vma.c:2421 [inline]
 __mmap_new_vma mm/vma.c:2484 [inline]
 __mmap_region mm/vma.c:2708 [inline]
 mmap_region+0x1045/0x1410 mm/vma.c:2786
 do_mmap+0x9b3/0xbe0 mm/mmap.c:558
 vm_mmap_pgoff+0x17a/0x2e0 mm/util.c:581
 ksys_mmap_pgoff+0x268/0x310 mm/mmap.c:604
 x64_sys_call+0x16bb/0x3000 arch/x86/include/generated/asm/syscalls_64.h:10
 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 0xffff88812279f1a0 of 8 bytes by task 12005 on cpu 0:
 __perf_update_times kernel/events/core.c:720 [inline]
 perf_event_update_time kernel/events/core.c:735 [inline]
 perf_event_set_state+0x153/0x440 kernel/events/core.c:754
 event_sched_out+0x2d4/0x4d0 kernel/events/core.c:2391
 group_sched_out kernel/events/core.c:2415 [inline]
 __pmu_ctx_sched_out+0x3e7/0x530 kernel/events/core.c:3458
 ctx_sched_out+0x273/0x2d0 kernel/events/core.c:3539
 task_ctx_sched_out+0x4d/0x70 kernel/events/core.c:2859
 perf_event_context_sched_out kernel/events/core.c:3746 [inline]
 __perf_event_task_sched_out+0x286/0x370 kernel/events/core.c:3846
 perf_event_task_sched_out include/linux/perf_event.h:1654 [inline]
 prepare_task_switch kernel/sched/core.c:5045 [inline]
 context_switch kernel/sched/core.c:5201 [inline]
 __schedule+0xbf0/0xcd0 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x5f/0xd0 kernel/sched/core.c:6960
 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:7017
 __mutex_lock_common kernel/locking/mutex.c:692 [inline]
 __mutex_lock+0x4ff/0xe20 kernel/locking/mutex.c:776
 __mutex_lock_slowpath+0xa/0x10 kernel/locking/mutex.c:1065
 mutex_lock+0x89/0x90 kernel/locking/mutex.c:290
 perf_poll+0x180/0x1f0 kernel/events/core.c:6150
 vfs_poll include/linux/poll.h:82 [inline]
 select_poll_one fs/select.c:480 [inline]
 do_select+0x8f1/0xf40 fs/select.c:536
 core_sys_select+0x3dc/0x6e0 fs/select.c:677
 do_pselect fs/select.c:759 [inline]
 __do_sys_pselect6 fs/select.c:798 [inline]
 __se_sys_pselect6+0x213/0x280 fs/select.c:789
 __x64_sys_pselect6+0x78/0x90 fs/select.c:789
 x64_sys_call+0x2e98/0x3000 arch/x86/include/generated/asm/syscalls_64.h:271
 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: 0x000000000038c145 -> 0x00000000003929d3

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 12005 Comm: syz.4.2772 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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