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Subject[perf] more perf_fuzzer memory corruption

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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