linux-kernel - Re: [perf] more perf_fuzzer memory corruption

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Message-ID: <alpine.DEB.2.02.1404152348160.22697@ionos.tec.linutronix.de>
Date:	Tue, 15 Apr 2014 23:49:39 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Vince Weaver <vincent.weaver@...ne.edu>
cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [perf] more perf_fuzzer memory corruption

On Tue, 15 Apr 2014, Vince Weaver wrote:
> 
> Still tracking memory corruption bugs found by the perf_fuzzer, I have 
> about 10 different log splats that I think might all be related to the 
> same underlying problem.
> 
> Anyway I managed to trigger this using the perf_fuzzer:
> 
> [  221.065278] Slab corruption (Not tainted): kmalloc-2048 start=ffff8800cd15e800, len=2048
> [  221.074062] 040: 6b 6b 6b 6b 6b 6b 6b 6b 98 72 57 cd 00 88 ff ff  kkkkkkkk.rW.....
> [  221.082321] Prev obj: start=ffff8800cd15e000, len=2048
> [  221.087933] 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
> [  221.096224] 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
> 
> And luckily I had ftrace running at the time.
> 
> The allocation of this block is by perf_event
> 
> perf_fuzzer-2520  [001]   182.980563: kmalloc:              (perf_event_alloc+0x55) call_site=ffffffff811399b5 ptr=0xffff8800cd15e800 bytes_req=1272 bytes_alloc=2048 gfp_flags=GFP_KERNEL|GFP_ZERO
> perf_fuzzer-2520  [000]   183.628515: kmalloc:              (perf_event_alloc+0x55) call_site=ffffffff811399b5 ptr=0xffff8800cd15e800 bytes_req=1272 bytes_alloc=2048 gfp_flags=GFP_KERNEL|GFP_ZERO
> perf_fuzzer-2520  [000]   183.628521: kfree:                (perf_event_alloc+0x2f7) call_site=ffffffff81139c57 ptr=0xffff8800cd15e800
> perf_fuzzer-2520  [000]   183.628844: kmalloc:              (perf_event_alloc+0x55) call_site=ffffffff811399b5 ptr=0xffff8800cd15e800 bytes_req=1272 bytes_alloc=2048 gfp_flags=GFP_KERNEL|GFP_ZERO
> ...(thousands of times of kmalloc/kfree)
> 
> Is it worth wading through this mess to try to track down what happened?

Definitely worth a try. Can you upload the trace file and provide the
URL or send it offlist in private mail if you cannot provide a public URL.

Thanks,

	tglx
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