Re: [RFC/PATCH] perf/core: Use POLLHUP for a pinned event in error
From: Namhyung Kim
Date: Mon Jun 02 2025 - 13:32:19 EST
Hello,
On Mon, Jun 02, 2025 at 10:10:47PM +0800, Lai, Yi wrote:
> Hi Namhyung Kim,
>
> Greetings!
>
> I used Syzkaller and found that there is WARNING: locking bug in perf_event_wakeup in linux-next next-20250530.
>
> After bisection and the first bad commit is:
> "
> f4b07fd62d4d perf/core: Use POLLHUP for pinned events in error
> "
>
> All detailed into can be found at:
> https://github.com/laifryiee/syzkaller_logs/tree/main/250601_162355_perf_event_wakeup
> Syzkaller repro code:
> https://github.com/laifryiee/syzkaller_logs/tree/main/250601_162355_perf_event_wakeup/repro.c
> Syzkaller repro syscall steps:
> https://github.com/laifryiee/syzkaller_logs/tree/main/250601_162355_perf_event_wakeup/repro.prog
> Syzkaller report:
> https://github.com/laifryiee/syzkaller_logs/tree/main/250601_162355_perf_event_wakeup/repro.report
> Kconfig(make olddefconfig):
> https://github.com/laifryiee/syzkaller_logs/tree/main/250601_162355_perf_event_wakeup/kconfig_origin
> Bisect info:
> https://github.com/laifryiee/syzkaller_logs/tree/main/250601_162355_perf_event_wakeup/bisect_info.log
> bzImage:
> https://github.com/laifryiee/syzkaller_logs/raw/refs/heads/main/250601_162355_perf_event_wakeup/bzImage_next-20250530
> Issue dmesg:
> https://github.com/laifryiee/syzkaller_logs/blob/main/250601_162355_perf_event_wakeup/next-20250530_dmesg.log
>
> "
> [ 39.913691] =============================
> [ 39.914157] [ BUG: Invalid wait context ]
> [ 39.914623] 6.15.0-next-20250530-next-2025053 #1 Not tainted
> [ 39.915271] -----------------------------
> [ 39.915731] repro/837 is trying to lock:
> [ 39.916191] ffff88801acfabd8 (&event->waitq){....}-{3:3}, at: __wake_up+0x26/0x60
> [ 39.917182] other info that might help us debug this:
> [ 39.917761] context-{5:5}
> [ 39.918079] 4 locks held by repro/837:
> [ 39.918530] #0: ffffffff8725cd00 (rcu_read_lock){....}-{1:3}, at: __perf_event_task_sched_in+0xd1/0xbc0
> [ 39.919612] #1: ffff88806ca3c6f8 (&cpuctx_lock){....}-{2:2}, at: __perf_event_task_sched_in+0x1a7/0xbc0
> [ 39.920748] #2: ffff88800d91fc18 (&ctx->lock){....}-{2:2}, at: __perf_event_task_sched_in+0x1f9/0xbc0
> [ 39.921819] #3: ffffffff8725cd00 (rcu_read_lock){....}-{1:3}, at: perf_event_wakeup+0x6c/0x470
> [ 39.922823] stack backtrace:
> [ 39.923171] CPU: 0 UID: 0 PID: 837 Comm: repro Not tainted 6.15.0-next-20250530-next-2025053 #1 PREEMPT(voluntary)
> [ 39.923196] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.o4
> [ 39.923214] Call Trace:
> [ 39.923221] <TASK>
> [ 39.923228] dump_stack_lvl+0xea/0x150
> [ 39.923256] dump_stack+0x19/0x20
> [ 39.923276] __lock_acquire+0xb22/0x22a0
> [ 39.923308] ? x86_pmu_commit_txn+0x195/0x2b0
> [ 39.923339] ? __lock_acquire+0x412/0x22a0
> [ 39.923375] lock_acquire+0x170/0x310
> [ 39.923407] ? __wake_up+0x26/0x60
> [ 39.923448] _raw_spin_lock_irqsave+0x52/0x80
> [ 39.923473] ? __wake_up+0x26/0x60
> [ 39.923504] __wake_up+0x26/0x60
> [ 39.923537] perf_event_wakeup+0x14a/0x470
> [ 39.923571] merge_sched_in+0x846/0x15c0
> [ 39.923610] visit_groups_merge.constprop.0.isra.0+0x952/0x1420
> [ 39.923653] ? __pfx_visit_groups_merge.constprop.0.isra.0+0x10/0x10
> [ 39.923688] ? sched_clock_noinstr+0x12/0x20
> [ 39.923724] ? __sanitizer_cov_trace_const_cmp1+0x1e/0x30
> [ 39.923766] ctx_sched_in+0x471/0xa20
> [ 39.923804] ? __pfx_ctx_sched_in+0x10/0x10
> [ 39.923838] ? __sanitizer_cov_trace_const_cmp4+0x1a/0x20
> [ 39.923878] perf_event_sched_in+0x47/0xa0
> [ 39.923912] __perf_event_task_sched_in+0x3fc/0xbc0
> [ 39.923951] ? __pfx___perf_event_task_sched_in+0x10/0x10
> [ 39.923984] ? __this_cpu_preempt_check+0x21/0x30
> [ 39.924012] ? __sanitizer_cov_trace_cmp8+0x1c/0x30
> [ 39.924046] ? xfd_validate_state+0x14f/0x1b0
> [ 39.924081] finish_task_switch.isra.0+0x525/0x990
> [ 39.924117] ? lock_unpin_lock+0xdc/0x170
> [ 39.924152] __schedule+0xef3/0x3840
> [ 39.924185] ? __pfx___schedule+0x10/0x10
> [ 39.924218] ? ktime_get_coarse_real_ts64+0xad/0xf0
> [ 39.924259] schedule+0xf6/0x3d0
> [ 39.924285] exit_to_user_mode_loop+0x7a/0x110
> [ 39.924315] do_syscall_64+0x284/0x2e0
> [ 39.924340] entry_SYSCALL_64_after_hwframe+0x76/0x7e
> [ 39.924360] RIP: 0033:0x7ff14103ee5d
> [ 39.924381] Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 8
> [ 39.924400] RSP: 002b:00007fffb2745578 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
> [ 39.924418] RAX: 0000000000000346 RBX: 0000000000000000 RCX: 00007ff14103ee5d
> [ 39.924431] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000082000
> [ 39.924443] RBP: 00007fffb27455c0 R08: 0000000000000000 R09: 0000000000000000
> [ 39.924456] R10: 0000000000000000 R11: 0000000000000202 R12: 00007fffb27459a8
> [ 39.924468] R13: 0000000000404e78 R14: 0000000000406e08 R15: 00007ff141389000
> [ 39.924497] </TASK>
> [ 40.307815] coredump: 804(repro): over core_pipe_limit, skipping core dump
> [ 40.472093] coredump: 795(repro): over core_pipe_limit, skipping core dump
> [ 40.545575] coredump: 799(repro): over core_pipe_limit, skipping core dump
> [ 40.948915] coredump: 833(repro): over core_pipe_limit, skipping core dump
> [ 40.989336] coredump: 811(repro): over core_pipe_limit, skipping core dump
> [ 42.121469] coredump: 857(repro): over core_pipe_limit, skipping core dump
> "
>
> Hope this cound be insightful to you.
>
> Regards,
> Yi Lai
>
> ---
>
> If you don't need the following environment to reproduce the problem or if you
> already have one reproduced environment, please ignore the following information.
>
> How to reproduce:
> git clone https://gitlab.com/xupengfe/repro_vm_env.git
> cd repro_vm_env
> tar -xvf repro_vm_env.tar.gz
> cd repro_vm_env; ./start3.sh // it needs qemu-system-x86_64 and I used v7.1.0
> // start3.sh will load bzImage_2241ab53cbb5cdb08a6b2d4688feb13971058f65 v6.2-rc5 kernel
> // You could change the bzImage_xxx as you want
> // Maybe you need to remove line "-drive if=pflash,format=raw,readonly=on,file=./OVMF_CODE.fd \" for different qemu version
> You could use below command to log in, there is no password for root.
> ssh -p 10023 root@localhost
>
> After login vm(virtual machine) successfully, you could transfer reproduced
> binary to the vm by below way, and reproduce the problem in vm:
> gcc -pthread -o repro repro.c
> scp -P 10023 repro root@localhost:/root/
>
> Get the bzImage for target kernel:
> Please use target kconfig and copy it to kernel_src/.config
> make olddefconfig
> make -jx bzImage //x should equal or less than cpu num your pc has
>
> Fill the bzImage file into above start3.sh to load the target kernel in vm.
>
>
> Tips:
> If you already have qemu-system-x86_64, please ignore below info.
> If you want to install qemu v7.1.0 version:
> git clone https://github.com/qemu/qemu.git
> cd qemu
> git checkout -f v7.1.0
> mkdir build
> cd build
> yum install -y ninja-build.x86_64
> yum -y install libslirp-devel.x86_64
> ../configure --target-list=x86_64-softmmu --enable-kvm --enable-vnc --enable-gtk --enable-sdl --enable-usb-redir --enable-slirp
> make
> make install
Thanks for the detailed instruction. I was able to reproduce it with
your setup. The below patch fixes it for me. Can you please double
check if it works well for you?
Thanks,
Namhyung
---8---
diff --git a/kernel/events/core.c b/kernel/events/core.c
index f34c99f8ce8f446a..e22eb88eb105b95b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3995,7 +3995,8 @@ static int merge_sched_in(struct perf_event *event, void *data)
if (*perf_event_fasync(event))
event->pending_kill = POLL_ERR;
- perf_event_wakeup(event);
+ event->pending_wakeup = 1;
+ irq_work_queue(&event->pending_irq);
} else {
struct perf_cpu_pmu_context *cpc = this_cpc(event->pmu_ctx->pmu);
--
2.49.0.1204.g71687c7c1d-goog