[moderation] [perf?] KCSAN: data-race in perf_event_set_state / perf_mmap_rb

[syzbot]

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=d2802c74daea3dc54249
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [ac...@kernel.org adrian...@intel.com alexander...@linux.intel.com iro...@google.com james...@linaro.org jo...@kernel.org linux-...@vger.kernel.org linux-pe...@vger.kernel.org mark.r...@arm.com mi...@redhat.com namh...@kernel.org pet...@infradead.org]

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+d2802c...@syzkaller.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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