linux-kernel - Re: sw_perf_event_destroy() oops while fuzzing

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Date:	Sat, 13 Apr 2013 21:40:53 +0300
From:	Tommi Rantala <tt.rantala@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: sw_perf_event_destroy() oops while fuzzing

2013/4/12 Tommi Rantala <tt.rantala@...il.com>:
> 2013/4/12 Peter Zijlstra <a.p.zijlstra@...llo.nl>:
>> perf_swevent_init() only sets event->destroy() (to
>> sw_perf_event_destroy) _after_ it increments the static key thing and
>> enqueues (and allocates) the hash list stuff.
>>
>> Obviously something is funny, but I'm not seeing it.
>
> Might this help... ? (untested)

I can reproduce the bug on my machine with:

#include <unistd.h>
#include <sys/syscall.h>
#include <linux/perf_event.h>

int main(void)
{
        struct perf_event_attr attr = {
                .type = PERF_TYPE_SOFTWARE,
                .size = sizeof(struct perf_event_attr),
                .config = 0x00000000ffffffff,
        };

        syscall(__NR_perf_event_open, &attr, getpid(), -1, -1, 0);
        return 0;
}

The patch below fixes the oops. I'll send it properly.

> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 59412d0..fff6420 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5330,7 +5330,7 @@ static void sw_perf_event_destroy(struct
> perf_event *event)
>
>  static int perf_swevent_init(struct perf_event *event)
>  {
> -       int event_id = event->attr.config;
> +       u64 event_id = event->attr.config;
>
>         if (event->attr.type != PERF_TYPE_SOFTWARE)
>                 return -ENOENT;
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