linux-kernel - Re: [PATCH] Out-of-bounds access in get_wchan (arch/x86/kernel/process

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>] [day] [month] [year] [list]

Message-ID: <CACT4Y+aV3dvcDJGH3+2EGDYzdFrWAMWNNLYWgyhgg4dFGhV4_w@mail.gmail.com>
Date:	Fri, 27 Sep 2013 12:35:27 -0700
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Wolfram Gloger <wmglo@...t.med.uni-muenchen.de>
Cc:	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kees <kees@...flux.net>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Out-of-bounds access in get_wchan (arch/x86/kernel/process_64.c)

On Fri, Sep 13, 2013 at 3:03 AM, Wolfram Gloger
<wmglo@...t.med.uni-muenchen.de> wrote:
> "H. Peter Anvin" <hpa@...or.com> writes:
>
>> Actually, the sanest would be:
>>
>>       if (fp  < (unsigned long)stack ||
>>           fp >= (unsigned long)stack+(THREAD_SIZE-16))
>>
>> ... wouldn't it (since we are accessing an 8-byte datum at offset +8?
>
> Ok, splitting hairs maybe, what about this V2 of the patch?
>
> fp is under userspace control.  stack-8 cannot underflow, otherwise we'd
> have much more serious problems in kernel space.
>
> Hence, for dereferencing fp+8:
>
> The case fp == stack-8 is valid.
> As is the case fp == stack+(THREAD_SIZE-16).
> Everything outside is invalid.
>
> About the worst-case implications: Like I said I have not reproduced it
> and cannot really comment on that.


+kees@, linux-kernel@
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/