Commit ed0dfffd authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

udp: fix potential infinite loop in SO_REUSEPORT logic 



Using a combination of connected and un-connected sockets, Dmitry
was able to trigger soft lockups with his fuzzer.

The problem is that sockets in the SO_REUSEPORT array might have
different scores.

Right after sk2=socket(), setsockopt(sk2,...,SO_REUSEPORT, on) and
bind(sk2, ...), but _before_ the connect(sk2) is done, sk2 is added into
the soreuseport array, with a score which is smaller than the score of
first socket sk1 found in hash table (I am speaking of the regular UDP
hash table), if sk1 had the connect() done, giving a +8 to its score.

hash bucket [X] -> sk1 -> sk2 -> NULL

sk1 score = 14  (because it did a connect())
sk2 score = 6

SO_REUSEPORT fast selection is an optimization. If it turns out the
score of the selected socket does not match score of first socket, just
fallback to old SO_REUSEPORT logic instead of trying to be too smart.

Normal SO_REUSEPORT users do not mix different kind of sockets, as this
mechanism is used for load balance traffic.

Fixes: e32ea7e7 ("soreuseport: fast reuseport UDP socket selection")
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Craig Gallek <kraigatgoog@gmail.com>
Acked-by: default avatarCraig Gallek <kraig@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a200dcb3

net/ipv4/udp.c

+21 −11
Original line number Diff line number Diff line
@@ -499,6 +499,7 @@ static struct sock *udp4_lib_lookup2(struct net *net, 
	struct sock *sk, *result;

	struct hlist_nulls_node *node;

	int score, badness, matches = 0, reuseport = 0;

	bool select_ok = true;

	u32 hash = 0;



begin:
@@ -512,15 +513,19 @@ begin: 
			badness = score;

			reuseport = sk->sk_reuseport;

			if (reuseport) {

				struct sock *sk2;

				hash = udp_ehashfn(net, daddr, hnum,

						   saddr, sport);

				if (select_ok) {

					struct sock *sk2;



					sk2 = reuseport_select_sock(sk, hash, skb,

							sizeof(struct udphdr));

					if (sk2) {

						result = sk2;

						select_ok = false;

						goto found;

					}

				}

				matches = 1;

			}

		} else if (score == badness && reuseport) {
@@ -563,6 +568,7 @@ struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr, 
	unsigned int hash2, slot2, slot = udp_hashfn(net, hnum, udptable->mask);

	struct udp_hslot *hslot2, *hslot = &udptable->hash[slot];

	int score, badness, matches = 0, reuseport = 0;

	bool select_ok = true;

	u32 hash = 0;



	rcu_read_lock();
@@ -601,15 +607,19 @@ begin: 
			badness = score;

			reuseport = sk->sk_reuseport;

			if (reuseport) {

				struct sock *sk2;

				hash = udp_ehashfn(net, daddr, hnum,

						   saddr, sport);

				if (select_ok) {

					struct sock *sk2;



					sk2 = reuseport_select_sock(sk, hash, skb,

							sizeof(struct udphdr));

					if (sk2) {

						result = sk2;

						select_ok = false;

						goto found;

					}

				}

				matches = 1;

			}

		} else if (score == badness && reuseport) {

net/ipv6/udp.c

+21 −11
Original line number Diff line number Diff line
@@ -257,6 +257,7 @@ static struct sock *udp6_lib_lookup2(struct net *net, 
	struct sock *sk, *result;

	struct hlist_nulls_node *node;

	int score, badness, matches = 0, reuseport = 0;

	bool select_ok = true;

	u32 hash = 0;



begin:
@@ -270,15 +271,19 @@ begin: 
			badness = score;

			reuseport = sk->sk_reuseport;

			if (reuseport) {

				struct sock *sk2;

				hash = udp6_ehashfn(net, daddr, hnum,

						    saddr, sport);

				if (select_ok) {

					struct sock *sk2;



					sk2 = reuseport_select_sock(sk, hash, skb,

							sizeof(struct udphdr));

					if (sk2) {

						result = sk2;

						select_ok = false;

						goto found;

					}

				}

				matches = 1;

			}

		} else if (score == badness && reuseport) {
@@ -321,6 +326,7 @@ struct sock *__udp6_lib_lookup(struct net *net, 
	unsigned int hash2, slot2, slot = udp_hashfn(net, hnum, udptable->mask);

	struct udp_hslot *hslot2, *hslot = &udptable->hash[slot];

	int score, badness, matches = 0, reuseport = 0;

	bool select_ok = true;

	u32 hash = 0;



	rcu_read_lock();
@@ -358,15 +364,19 @@ begin: 
			badness = score;

			reuseport = sk->sk_reuseport;

			if (reuseport) {

				struct sock *sk2;

				hash = udp6_ehashfn(net, daddr, hnum,

						    saddr, sport);

				if (select_ok) {

					struct sock *sk2;



					sk2 = reuseport_select_sock(sk, hash, skb,

							sizeof(struct udphdr));

					if (sk2) {

						result = sk2;

						select_ok = false;

						goto found;

					}

				}

				matches = 1;

			}

		} else if (score == badness && reuseport) {

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