linux-kernel - Re: [RFC] [PATCH] cpuset operations causes Badness at mm/slab.c:777 warning

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 for Android: free password hash cracker in your pocket

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

Message-Id: <20070601151649.bb23c6f9.akpm@linux-foundation.org>
Date:	Fri, 1 Jun 2007 15:16:49 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Christoph Lameter <clameter@....com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Srinivasa Ds <srinivasa@...ibm.com>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Dinakar Guniguntala <dino@...ibm.com>, pj@....com,
	simon.derr@...l.net, clameter@...ulhu.engr.sgi.com,
	rientjes@...gle.com
Subject: Re: [RFC] [PATCH] cpuset operations causes Badness at mm/slab.c:777
 warning

On Fri, 1 Jun 2007 14:45:27 -0700 (PDT)
Christoph Lameter <clameter@....com> wrote:

> On Fri, 1 Jun 2007, Andrew Morton wrote:
> 
> > Poisoning and redzoning could have caught that.
> 
> Redzoning would not have caught it. This was a kmalloc allocation and 
> SLAB always gave them 32 bytes to play with. Only writes more than 32 
> bytes behind would have been caught.
> 
> Poisoning is only applicable to unallocated objects and these were 
> allocated.

Nope and nope.

This is a special case where the user asked for zero bytes and the kernel
gave him 8 (or 32) bytes instead.

If slab was smart enough, it would have poisoned those 8 bytes to some
known pattern, and then checked that they still had that pattern when the
memory got freed again.

But it isn't smart enough, so the bug went undetected.

As I said, it's specific to the kmalloc(0) problem, and we're fixing that
by other means anyway.

-
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/