Re: perf: use after free in perf_remove_from_context

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

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On 05/14/2014 12:35 PM, Peter Zijlstra wrote:
> On Wed, May 14, 2014 at 12:32:26PM -0400, Sasha Levin wrote:
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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 ;-)
> 

./trinity -xinit_module -xreboot -xshutdown -xunshare -xnfsservctl -xclock_nanosleep -xuselib -xumount -xmount -m --quiet --dangerous -C 400 -l off

Note that I run it as root in a disposable VM. Running that as root on your
machine will likely kill it.


Thanks,
Sasha
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