Re: [patch v2] sunrpc: integer underflow in rsc_parse()

J. Bruce Fields
2015-02-26T20:40:46Z

On Tue, Feb 24, 2015 at 10:54:44PM -0500, Simo Sorce wrote:
> On Tue, 2015-02-24 at 18:34 +0300, Dan Carpenter wrote:
> > If we call groups_alloc() with invalid values then it's might lead to
> > memory corruption. For example, with a negative value then we might not
> > allocate enough for sizeof(struct group_info).
> >
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> > v2: In v1, I changed groups_alloc(). The other places which call
> > groups_alloc() check the value before calling. Eric wanted that, either
> > have all the callers check, or all the callers rely on groups_alloc().
> > In the end, Bruce Fields said adding the check here was probably
> > reasonable.
> >
> > diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
> > index 224a82f..1095be9 100644
> > --- a/net/sunrpc/auth_gss/svcauth_gss.c
> > +++ b/net/sunrpc/auth_gss/svcauth_gss.c
> > @@ -463,6 +463,8 @@ static int rsc_parse(struct cache_detail *cd,
> > /* number of additional gid's */
> > if (get_int(&mesg, &N))
> > goto out;
> > + if (N < 0 || N > NGROUPS_MAX)
> > + goto out;
> > status = -ENOMEM;
> > rsci.cred.cr_group_info = groups_alloc(N);
> > if (rsci.cred.cr_group_info = NULL)
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
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>
> I touched this code relatively recently, and this check looks correct.
> Feel free to add Reviewed-by: Simo Sorce <simo@redhat.com>

Thanks! I thought your below-the-line context was useful, so pulled a
version of it into the commit.

--b.

commit 76cb4be993c0
Author: Dan Carpenter <dan.carpenter@oracle.com>
Date: Tue Feb 24 18:34:01 2015 +0300

sunrpc: integer underflow in rsc_parse()

If we call groups_alloc() with invalid values then it's might lead to
memory corruption. For example, with a negative value then we might not
allocate enough for sizeof(struct group_info).

(We're doing this in the caller for consistency with other callers of
groups_alloc(). The other alternative might be to move the check out of
all the callers into groups_alloc().)

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 224a82f24d3c..1095be9c80ab 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -463,6 +463,8 @@ static int rsc_parse(struct cache_detail *cd,
/* number of additional gid's */
if (get_int(&mesg, &N))
goto out;
+ if (N < 0 || N > NGROUPS_MAX)
+ goto out;
status = -ENOMEM;
rsci.cred.cr_group_info = groups_alloc(N);
if (rsci.cred.cr_group_info = NULL)