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SubjectRe: keys: GPF in request_key
Date
Dmitry Vyukov <dvyukov@google.com> wrote:

> Code: 41 54 49 89 f4 53 49 89 d7 48 89 fb 48 83 ec 08 e8 d1 50 67 ff
> 49 8d 7c 24 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80>
> 3c 02 00 0f 85 35 02 00 00 49 83 7c 24 10 00 0f 84 bb 01 00

This disassembles to:

0: 41 54 push %r12
2: 49 89 f4 mov %rsi,%r12
5: 53 push %rbx
6: 49 89 d7 mov %rdx,%r15
9: 48 89 fb mov %rdi,%rbx
c: 48 83 ec 08 sub $0x8,%rsp
10: e8 d1 50 67 ff callq 0xffffffffff6750e6
15: 49 8d 7c 24 10 lea 0x10(%r12),%rdi
1a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
21: fc ff df
24: 48 89 fa mov %rdi,%rdx
27: 48 c1 ea 03 shr $0x3,%rdx
2b:* 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
2f: 0f 85 35 02 00 00 jne 0x26a
35: 49 83 7c 24 10 00 cmpq $0x0,0x10(%r12)
3b: 0f .byte 0xf
3c: 84 .byte 0x84
3d: bb .byte 0xbb
3e: 01 00 add %eax,(%rax)

I can see that RAX got loaded from the instruction at 0x1a, but the code
doesn't look very much like what I get out of the compiler (your compiled
function is also at least double the size of what I get, presumably due to
kasan?).

Can you disassemble __key_link_begin() for me and send me your config?

In particular, 0xdffffc0000000000 looks very weird. Is this code validating
the pointer in R12?

David

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