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

[Simo Sorce <simo@redhat.com>]

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)
> --
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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>

Simo.

-- 
Simo Sorce * Red Hat, Inc * New York