KCSAN: data-race in __se_sys_perf_event_open / find_get_context

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c4681547 Linux 5.13-rc3
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a3dd4bd00000
kernel config: https://syzkaller.appspot.com/x/.config?x=3bcc8a6b51ef8094
dashboard link: https://syzkaller.appspot.com/bug?extid=c611b5beb8dec04ff9b2
compiler: Debian clang version 11.0.1-2
CC: [ac...@kernel.org alexander...@linux.intel.com and...@kernel.org a...@kernel.org b...@vger.kernel.org dan...@iogearbox.net john.fa...@gmail.com jo...@redhat.com ka...@fb.com kps...@kernel.org linux-...@vger.kernel.org linux-pe...@vger.kernel.org mark.r...@arm.com mi...@redhat.com namh...@kernel.org net...@vger.kernel.org pet...@infradead.org songliu...@fb.com y...@fb.com]

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+c611b5...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __se_sys_perf_event_open / find_get_context

write to 0xffff888237c2d520 of 4 bytes by task 29834 on cpu 1:
find_get_context+0x310/0x5c0 kernel/events/core.c:4612
__do_sys_perf_event_open kernel/events/core.c:12085 [inline]
__se_sys_perf_event_open+0x85e/0x2740 kernel/events/core.c:11921
__x64_sys_perf_event_open+0x63/0x70 kernel/events/core.c:11921
do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237c2d520 of 4 bytes by task 29826 on cpu 0:
perf_unpin_context kernel/events/core.c:1520 [inline]
__do_sys_perf_event_open kernel/events/core.c:12351 [inline]
__se_sys_perf_event_open+0x1e84/0x2740 kernel/events/core.c:11921
__x64_sys_perf_event_open+0x63/0x70 kernel/events/core.c:11921
do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29826 Comm: syz-executor.3 Not tainted 5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[Marco Elver]

#syz fix: perf: Fix data race between pin_count increment/decrement

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