[perf] more perf_fuzzer memory corruption

[Vince Weaver]

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?

Vince

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