Re: [syzbot] WARNING in __perf_install_in_context

On Mon, May 17, 2021 at 01:27:49PM +0200, Peter Zijlstra wrote:

On Mon, May 17, 2021 at 03:56:22AM -0700, syzbot wrote:

quoted

Hello,

syzbot found the following issue on:

HEAD commit:    18a3c5f7 Merge tag 'for_linus' of git://git.kernel.org/pub..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes
console output: https://syzkaller.appspot.com/x/log.txt?x=1662c153d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b8ac1fe5995f69d7
dashboard link: https://syzkaller.appspot.com/bug?extid=0fb24f56fa707081e4f2
userspace arch: riscv64

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0fb24f56fa707081e4f2@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 8643 at kernel/events/core.c:2781 __perf_install_in_context+0x1c0/0x47c kernel/events/core.c:2781
Modules linked in:
CPU: 1 PID: 8643 Comm: syz-executor.0 Not tainted 5.12.0-rc8-syzkaller-00011-g18a3c5f7abfd #0
Hardware name: riscv-virtio,qemu (DT)

How serious should I take this thing? ARM64 and x86_64 don't show these
errors.

I think I've seen this in the past on arm64, but very rarely, and never
with a consistent reproducer.

I'm currently fuyzzing v5.13-rc1, and haven't hit anything like this
after ~5 days.

Thanks,
Mark.