linux-kernel - Re: security: oops on boot in __key_link

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Date:	Mon, 28 Jul 2014 12:32:12 +0100
From:	David Howells <dhowells@...hat.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	dhowells@...hat.com, James Morris <james.l.morris@...cle.com>,
	serge@...lyn.com, keyrings@...ux-nfs.org,
	linux-security-module@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: security: oops on boot in __key_link_begin

Sasha Levin <sasha.levin@...cle.com> wrote:

>   23:	49 89 9f f0 00 00 00 	mov    %rbx,0xf0(%r15)
>   2a:	55                   	push   %rbp
>   2b:*	c1 b8 42 ff 49 8b 5f 	sarl   $0x5f,-0x74b600be(%rax)		<-- trapping instruction
>   32:	10 49 8d             	adc    %cl,-0x73(%rcx)

I can't make any sense of this.  It doesn't look anything like what I
get when I disassemble assoc_array_insert().  There are no SARL or ADC
instructions.

Can you load your vmlinux into gdb and disassemble the function that holds the
faulting instruction:

	gdb vmlinux
	(gdb) disassemble <RIP-value>

Unfortunately, I'm not sure what the RIP value actually is because it's been
replaced in the dump by source file + line number.  It's not this:

	[   31.330473] CR2: ffffffff8b49ff42

though.  That's RAX (ie. 0) plus the offset in the following instruction:

	sarl   $0x5f,-0x74b600be(%rax)		<-- trapping instruction

David
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