net: ice: Fix potential NULL pointer dereference in ice_bridge_setlink()

The function ice_bridge_setlink() may encounter a NULL pointer dereference
if nlmsg_find_attr() returns NULL and br_spec is dereferenced subsequently
in nla_for_each_nested(). To address this issue, add a check to ensure that
br_spec is not NULL before proceeding with the nested attribute iteration.

Fixes: b1edc14a ("ice: Implement ice_bridge_getlink and ice_bridge_setlink")
Signed-off-by: Rand Deeb <rand.sec96@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/ice/ice_main.c

@@ -8013,6 +8013,8 @@ ice_bridge_setlink(struct net_device *dev, struct nlmsghdr *nlh,
 	pf_sw = pf->first_sw;
 	/* find the attribute in the netlink message */
 	br_spec = nlmsg_find_attr(nlh, sizeof(struct ifinfomsg), IFLA_AF_SPEC);
+	if (!br_spec)
+		return -EINVAL;
 
 	nla_for_each_nested(attr, br_spec, rem) {
 		__u16 mode;