2014-12-22 17:37 GMT+03:00 Sasha Levin <sasha.levin@xxxxxxxxxx>:
> Hi all,
>
> While fuzzing with trinity inside a KVM tools guest running the latest -next
> kernel, I've stumbled on the following spew:
>
> [ 2015.960381] general protection fault: 0000 [#1] PREEMPT SMP KASAN
Actually this is NULL-ptr dereference. Since you are using kasan with
inline instrumentation
NULL-ptr deref transforms into GPF.
> [ 2015.970534] RAX: 0000000000000000 RBX: ffff88000003a960 RCX: 0000000000000073
> [ 2015.970534] RDX: 1ffff10101c8f3c4 RSI: 0000000000000000 RDI: ffff88080e479e20
> [ 2015.970534] RBP: ffff88080e477a28 R08: 0000000000000066 R09: 0000000000000073
> [ 2015.970534] R10: ffffda0017d55630 R11: dfffe90000000000 R12: ffff88005fc644b8
> [ 2015.970534] R13: dfffe90000000000 R14: ffffffff92464884 R15: 0000000000000000
[...]
> All code
> ========
> 0: e8 03 42 80 3c callq 0x3c804208
> 5: 28 00 sub %al,(%rax)
> 7: 0f 85 ff 01 00 00 jne 0x20c
> d: 4c 8b 7b 18 mov 0x18(%rbx),%r15
> 11: 4d 85 ff test %r15,%r15
> 14: 0f 84 de 01 00 00 je 0x1f8
> 1a: 41 f6 c7 07 test $0x7,%r15b
> 1e: 0f 85 d4 01 00 00 jne 0x1f8
> 24: 4c 89 f8 mov %r15,%rax
> 27: 48 c1 e8 03 shr $0x3,%rax
> 2b:* 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
Three commands above are result of KASAN's instrumentation.
They check shadow for address in %r15:
if (*((%r15 >> 3) + kasan_shadow_offset)
> 30: 0f 85 b5 01 00 00 jne 0x1eb
> 36: 4d 8b 37 mov (%r15),%r14
And here is memory access, that KASAN checking.
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