Re: keys: GPF in request_key

[David Howells]

Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:

> The line causes the crash is:
>     BUG_ON(index_key->desc_len == 0);
> 
> The addresses that the line tried to access are:
>
> RDI: ffffffffca29fa68
> RDI: ffffffffd7236a28
> RDI: 000000007d19ed68

These are all calculated from R12:

	lea    0x10(%r12),%rdi
	...
	mov    %rdi,%rdx
	shr    $0x3,%rdx
	cmpb   $0x0,(%rdx,%rax,1)

R12 would appear to be index_key - which would correlate with 0x10 being the
offset of desc_len therein - but why muck around with the pointer rather than
just 

In my compiler output,

	BUG_ON(index_key->desc_len == 0);

is turned into:

   0xffffffff8131f023 <+0>:     cmpq   $0x0,0x10(%rsi)
   0xffffffff8131f028 <+5>:     jne    0xffffffff8131f02c <__key_link_begin+9>
   0xffffffff8131f02a <+7>:     ud2    

What compiler are you using?

David