netfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check()

Reject rt match rules whose addrnr exceeds IP6T_RT_HOPS.

rt_mt6() expects addrnr to stay within the bounds of rtinfo->addrs[].
Validate addrnr during rule installation so malformed rules are rejected
before the match logic can use an out-of-range value.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Reported-by: Yifan Wu <[email protected]>
Reported-by: Juefei Pu <[email protected]>
Co-developed-by: Yuan Tan <[email protected]>
Signed-off-by: Yuan Tan <[email protected]>
Suggested-by: Xin Liu <[email protected]>
Tested-by: Yuhang Zheng <[email protected]>
Signed-off-by: Ren Wei <[email protected]>
Signed-off-by: Florian Westphal <[email protected]>
Signed-off-by: Pablo Neira Ayuso <[email protected]>

Author: Ren Wei

net/ipv6/netfilter/ip6t_rt.c

@@ -157,6 +157,10 @@ static int rt_mt6_check(const struct xt_mtchk_param *par)
 		pr_debug("unknown flags %X\n", rtinfo->invflags);
 		return -EINVAL;
 	}
+	if (rtinfo->addrnr > IP6T_RT_HOPS) {
+		pr_debug("too many addresses specified\n");
+		return -EINVAL;
+	}
 	if ((rtinfo->flags & (IP6T_RT_RES | IP6T_RT_FST_MASK)) &&
 	    (!(rtinfo->flags & IP6T_RT_TYP) ||
 	     (rtinfo->rt_type != 0) ||