linux-kernel - Re: [PATCH] fs, dlm: Don't leak, don't do pointless NULL checks and use kzalloc

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]

Message-ID: <alpine.LNX.2.00.1106292344110.3747@swampdragon.chaosbits.net>
Date:	Wed, 29 Jun 2011 23:51:00 +0200 (CEST)
From:	Jesper Juhl <jj@...osbits.net>
To:	David Teigland <teigland@...hat.com>
cc:	linux-kernel@...r.kernel.org, cluster-devel@...hat.com,
	Christine Caulfield <ccaulfie@...hat.com>
Subject: Re: [PATCH] fs, dlm: Don't leak, don't do pointless NULL checks and
 use kzalloc

On Wed, 29 Jun 2011, David Teigland wrote:

> On Wed, Jun 29, 2011 at 11:09:27PM +0200, Jesper Juhl wrote:
> > In fs/dlm/lock.c in the dlm_scan_waiters() function there are 3 small
> > issues:
> > 
> > 1) first time through the loop we allocate memory for 'warned', if we
> > then (in the loop) don't take the "if (!warned)" path and loop again,
> > the second time through the loop we'll allocate memory again and store
> > it to 'warned' without freeing the previous allocation - this leaks
> > memory.
> 
> I don't think so; num_nodes won't be set to zero.
> 

Hmm. How so?  Maybe I'm missing something obvious, but;
num_nodes is initialized to zero at the beginning of the function, which 
means that we'll definately do the first allocation in the loop.
We then set num_nodes equal to ls->ls_num_nodes - what guarantees that 
this will not be zero so we won't do a second allocation (and leak) the 
second time through the loop?

> > 2) There's no need to test the return value of the allocation and do a
> > memset if is succeedes. Just use kzalloc() to obtain zeroed memory.
> 
> fine
> 
> > 3) Since kfree() handles NULL pointers gracefully, the test of
> > 'warned' against NULL before the kfree() after the loop is completely
> > pointless. Remove it.
> 
> fine
> 
> ack if you want to push those two out yourself.
> Dave

Ok. I can resend a patch (tomorrow) with just those two changes and will 
add your Acked-by:

-- 
Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
Don't top-post http://www.catb.org/jargon/html/T/top-post.html
Plain text mails only, please.

--
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/