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Commit ce723d8e authored by Julian Anastasov's avatar Julian Anastasov Committed by David S. Miller
Browse files

[IPV4]: Fix refcount damaging in net/ipv4/route.c 



	One such place that can damage the dst refcnts is route.c with
CONFIG_IP_ROUTE_MULTIPATH_CACHED enabled, i don't see the user's
.config. In this new code i see that rt_intern_hash is called before
dst->refcnt is set to 1, dst is the 2nd arg to rt_intern_hash.

Arg 2 of rt_intern_hash must come with refcnt 1 as it is added to
table or dropped depending on error/add/update. One such example is
ip_mkroute_input where __mkroute_input return rth with refcnt 0 which
is provided to rt_intern_hash. ip_mkroute_output looks like a 2nd such
place. Appending untested patch for comments and review.  The idea is
to put previous reference as we are going to return next result/error.

Signed-off-by: default avatarJulian Anastasov <ja@ssi.bg>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c921e4c4

net/ipv4/route.c

+14 −15
Original line number Diff line number Diff line
@@ -1760,6 +1760,7 @@ static inline int __mkroute_input(struct sk_buff *skb, 
		goto cleanup;

	}



	atomic_set(&rth->u.dst.__refcnt, 1);

	rth->u.dst.flags= DST_HOST;

#ifdef CONFIG_IP_ROUTE_MULTIPATH_CACHED

	if (res->fi->fib_nhs > 1)
@@ -1820,7 +1821,6 @@ static inline int ip_mkroute_input_def(struct sk_buff *skb, 
	err = __mkroute_input(skb, res, in_dev, daddr, saddr, tos, &rth);

	if (err)

		return err;

	atomic_set(&rth->u.dst.__refcnt, 1);



	/* put it into the cache */

	hash = rt_hash_code(daddr, saddr ^ (fl->iif << 5), tos);
@@ -1834,8 +1834,8 @@ static inline int ip_mkroute_input(struct sk_buff *skb, 
				   u32 daddr, u32 saddr, u32 tos)

{

#ifdef CONFIG_IP_ROUTE_MULTIPATH_CACHED

	struct rtable* rth = NULL;

	unsigned char hop, hopcount, lasthop;

	struct rtable* rth = NULL, *rtres;

	unsigned char hop, hopcount;

	int err = -EINVAL;

	unsigned int hash;
@@ -1844,8 +1844,6 @@ static inline int ip_mkroute_input(struct sk_buff *skb, 
	else

		hopcount = 1;



	lasthop = hopcount - 1;



	/* distinguish between multipath and singlepath */

	if (hopcount < 2)

		return ip_mkroute_input_def(skb, res, fl, in_dev, daddr,
@@ -1855,6 +1853,10 @@ static inline int ip_mkroute_input(struct sk_buff *skb, 
	for (hop = 0; hop < hopcount; hop++) {

		res->nh_sel = hop;



		/* put reference to previous result */

		if (hop)

			ip_rt_put(rtres);



		/* create a routing cache entry */

		err = __mkroute_input(skb, res, in_dev, daddr, saddr, tos,

				      &rth);
@@ -1863,7 +1865,7 @@ static inline int ip_mkroute_input(struct sk_buff *skb, 


		/* put it into the cache */

		hash = rt_hash_code(daddr, saddr ^ (fl->iif << 5), tos);

		err = rt_intern_hash(hash, rth, (struct rtable**)&skb->dst);

		err = rt_intern_hash(hash, rth, &rtres);

		if (err)

			return err;
@@ -1873,13 +1875,8 @@ static inline int ip_mkroute_input(struct sk_buff *skb, 
				     FIB_RES_NETMASK(*res),

				     res->prefixlen,

				     &FIB_RES_NH(*res));



		/* only for the last hop the reference count is handled

		 * outside

		 */

		if (hop == lasthop)

			atomic_set(&(skb->dst->__refcnt), 1);

	}

	skb->dst = &rtres->u.dst;

	return err;

#else /* CONFIG_IP_ROUTE_MULTIPATH_CACHED  */

	return ip_mkroute_input_def(skb, res, fl, in_dev, daddr, saddr, tos);
@@ -2208,6 +2205,7 @@ static inline int __mkroute_output(struct rtable **result, 
		goto cleanup;

	}		



	atomic_set(&rth->u.dst.__refcnt, 1);

	rth->u.dst.flags= DST_HOST;

#ifdef CONFIG_IP_ROUTE_MULTIPATH_CACHED

	if (res->fi) {
@@ -2290,8 +2288,6 @@ static inline int ip_mkroute_output_def(struct rtable **rp, 
	if (err == 0) {

		u32 tos = RT_FL_TOS(oldflp);



		atomic_set(&rth->u.dst.__refcnt, 1);

		

		hash = rt_hash_code(oldflp->fl4_dst, 

				    oldflp->fl4_src ^ (oldflp->oif << 5), tos);

		err = rt_intern_hash(hash, rth, rp);
@@ -2326,6 +2322,10 @@ static inline int ip_mkroute_output(struct rtable** rp, 
			dev2nexthop = FIB_RES_DEV(*res);

			dev_hold(dev2nexthop);



			/* put reference to previous result */

			if (hop)

				ip_rt_put(*rp);



			err = __mkroute_output(&rth, res, fl, oldflp,

					       dev2nexthop, flags);
@@ -2350,7 +2350,6 @@ static inline int ip_mkroute_output(struct rtable** rp, 
			if (err != 0)

				return err;

		}

		atomic_set(&(*rp)->u.dst.__refcnt, 1);

		return err;

	} else {

		return ip_mkroute_output_def(rp, res, fl, oldflp, dev_out,