linux-kernel - Re: WARNING: kernel stack frame pointer at ffffffff82e03f40 in swapper:0 has bad value (null)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 12 Dec 2016 22:34:46 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86-ml <x86@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: WARNING: kernel stack frame pointer at ffffffff82e03f40 in
 swapper:0 has bad value           (null)

On Mon, Dec 12, 2016 at 03:16:27PM -0600, Josh Poimboeuf wrote:
> I still can't figure out what could cause this, nor can I recreate it.

Want my .config?

> Andy, any idea?  I'm trying to figure out why a stack trace of the
> initial task, early in start_kernel(), would show start_cpu() on the
> stack *twice*.  The start_cpu() entry on the stack at ffffffffbce03f50
> is right where it's supposed to be.  But then there's another
> start_cpu() entry at 0xffffffffbce03f48 which is pointed to by the frame
> pointer chain.  I can't figure out where that one came from and why the
> stack is offset by a word, compared to all the other idle task stacks
> I've seen.

Btw, why do you have:

        call    1f              # put return address on stack for unwinder

there in start_cpu() instead of

	push $start_cpu

or so? That CALL looks strange there. If you want to put the return
address, just push start_cpu's address and that's it.

Or am I missing something?

> Boris, what kind of CPU is it?

[    0.169371] smpboot: CPU0: Intel(R) Xeon(R) CPU E5-1620 0 @ 3.60GHz (family: 0x6, model: 0x2d, stepping: 0x7)

Sandybridge. The model 0x2d corresponds to that INTEL_FAM6_SANDYBRIDGE_X
define in intel-family.h.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.