Re: [patch] groups: integer underflow in groups_alloc()

[bfields@fieldses.org (J. Bruce Fields)]

On Mon, Feb 23, 2015 at 09:03:27PM +0300, Dan Carpenter wrote:
> On Mon, Feb 23, 2015 at 11:10:02AM -0600, Eric W. Biederman wrote:
> > Dan Carpenter <dan.carpenter@oracle.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.

I think that's probably the correct check, sure.

Putting it in rsc_parse sounds reasonable.

--b.