linux-kernel - Re: [patch] groups: integer underflow in groups

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Date:	Mon, 23 Feb 2015 21:03:27 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Wang YanQing <udknight@...il.com>,
	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] groups: integer underflow in groups_alloc()

On Mon, Feb 23, 2015 at 11:10:02AM -0600, Eric W. Biederman wrote:
> Dan Carpenter <dan.carpenter@...cle.com> writes:
> 
> > This is called from rsc_parse() with a use controlled value.  Say for
> > example that "gidsetsize" is negative, then we could end up allocating
> > less than sizeof(struct group_info) leading to memory corruption.
> 
> Right now it is the responsibility of the caller of groups_alloc to make
> certain that gidsetsize is a valid value, and the callers of
> groups_alloc who know what they are doing already validate this value.
> 
> Either the pattern of caller validates the messages needs to continue,
> or groups_alloc needs to be changed and all of the callers need to be
> updated.
> 
> Changing groups_alloc for one particular caller is just going to cause
> maintenance problems.
> 

This only affects NFS so let's hear from them if this limit is correct
and decide from there.

regards,
dan carpenter

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