ipv4: potential underflow in compat_ip_setsockopt()

The value of "n" is capped at 0x1ffffff but it checked for negative
values.  I don't think this causes a problem but I'm not certain and
it's harmless to prevent it.

Fixes: 5b6d191426cd ("ipv4: do compat setsockopt for MCAST_MSFILTER directly")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index a2469bc57cfe85c240541152568b5b84bb4ff757..f43d5f12aa86afce60707fd24a1209ec9846b560 100644 (file)
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1347,8 +1347,8 @@ int compat_ip_setsockopt(struct sock *sk, int level, int optname,
        {
                const int size0 = offsetof(struct compat_group_filter, gf_slist);
                struct compat_group_filter *gf32;
+               unsigned int n;
                void *p;
-               int n;
 
                if (optlen < size0)
                        return -EINVAL;