Re: perf: use after free in perf_remove_from_context

[Sasha Levin <sasha.levin@oracle.com>]

On 05/14/2014 12:35 PM, Peter Zijlstra wrote:
> On Wed, May 14, 2014 at 12:32:26PM -0400, Sasha Levin wrote:
>> > -----BEGIN PGP SIGNED MESSAGE-----
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>> > On 05/14/2014 12:29 PM, Peter Zijlstra wrote:
>>> > > On Mon, May 12, 2014 at 11:42:33AM -0400, Sasha Levin wrote:
>>>> > >> Hi all,
>>>> > >> 
>>>> > >> While fuzzing with trinity inside a KVM tools guest running the latest -next kernel I've stumbled on the following spew. Maybe related to the very recent change in freeing on task exit?
>>>> > >> 
>>>> > >> [ 2509.827261] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 2509.830379] Dumping ftrace buffer: [ 2509.830379]    (ftrace buffer empty) [ 2509.830379] Modules linked in: [ 2509.830379] CPU: 47 PID: 43306 Comm: trinity-c126 Tainted: G        W     3.15.0-rc5-next-20140512-sasha-00019-ga20bc00-dirty #456
>>> > > 
>>> > > Any particular trinity setup? And would you happen to have the seed of that run?
>> > 
>> > Nothing special about trinity options. 400 threads and blacklisting some of the
>> > destructive syscalls (umount, reboot, etc).
>> > 
>> > I don't have the seed, but that problem did reproduce again tonight so I can test
>> > out debug code if you have something in mind.
> Nah, I drew a pretty big blank, which is why I wanted to see if I could
> reproduce. If you could share your trinity cmdline I'd be much obliged.
> While I did manage to clone (the repo moved since last time) and build
> it, I'm not really that handy with it and want to avoid destroying my
> machine if possible ;-)

Anything I could do to help out with this? It reproduces pretty easily on my
configuration so I'd be happy to test out whatever might help.


Thanks,
Sasha