From 69421bf98482d089e50799f45e48b25ce4a8d154 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Fri, 14 Oct 2022 11:26:25 -0700 Subject: udp: Update reuse->has_conns under reuseport_lock. When we call connect() for a UDP socket in a reuseport group, we have to update sk->sk_reuseport_cb->has_conns to 1. Otherwise, the kernel could select a unconnected socket wrongly for packets sent to the connected socket. However, the current way to set has_conns is illegal and possible to trigger that problem. reuseport_has_conns() changes has_conns under rcu_read_lock(), which upgrades the RCU reader to the updater. Then, it must do the update under the updater's lock, reuseport_lock, but it doesn't for now. For this reason, there is a race below where we fail to set has_conns resulting in the wrong socket selection. To avoid the race, let's split the reader and updater with proper locking. cpu1 cpu2 +----+ +----+ __ip[46]_datagram_connect() reuseport_grow() . . |- reuseport_has_conns(sk, true) |- more_reuse = __reuseport_alloc(more_socks_size) | . | | |- rcu_read_lock() | |- reuse = rcu_dereference(sk->sk_reuseport_cb) | | | | | /* reuse->has_conns == 0 here */ | | |- more_reuse->has_conns = reuse->has_conns | |- reuse->has_conns = 1 | /* more_reuse->has_conns SHOULD BE 1 HERE */ | | | | | |- rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb, | | | more_reuse) | `- rcu_read_unlock() `- kfree_rcu(reuse, rcu) | |- sk->sk_state = TCP_ESTABLISHED Note the likely(reuse) in reuseport_has_conns_set() is always true, but we put the test there for ease of review. [0] For the record, usually, sk_reuseport_cb is changed under lock_sock(). The only exception is reuseport_grow() & TCP reqsk migration case. 1) shutdown() TCP listener, which is moved into the latter part of reuse->socks[] to migrate reqsk. 2) New listen() overflows reuse->socks[] and call reuseport_grow(). 3) reuse->max_socks overflows u16 with the new listener. 4) reuseport_grow() pops the old shutdown()ed listener from the array and update its sk->sk_reuseport_cb as NULL without lock_sock(). shutdown()ed TCP sk->sk_reuseport_cb can be changed without lock_sock(), but, reuseport_has_conns_set() is called only for UDP under lock_sock(), so likely(reuse) never be false in reuseport_has_conns_set(). [0]: https://lore.kernel.org/netdev/CANn89iLja=eQHbsM_Ta2sQF0tOGU8vAGrh_izRuuHjuO1ouUag@mail.gmail.com/ Fixes: acdcecc61285 ("udp: correct reuseport selection with connected sockets") Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20221014182625.89913-1-kuniyu@amazon.com Signed-off-by: Paolo Abeni --- net/ipv6/udp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/ipv6/udp.c') diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 8d09f0ea5b8c..129ec5a9b0eb 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -195,7 +195,7 @@ static struct sock *udp6_lib_lookup2(struct net *net, result = lookup_reuseport(net, sk, skb, saddr, sport, daddr, hnum); /* Fall back to scoring if group has connections */ - if (result && !reuseport_has_conns(sk, false)) + if (result && !reuseport_has_conns(sk)) return result; result = result ? : sk; -- cgit v1.2.3-70-g09d2 From 8f279fb00bb29def9ac79e28c5d6d8e07d21f3fb Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Thu, 27 Oct 2022 00:25:56 +0100 Subject: udp: advertise ipv6 udp support for msghdr::ubuf_info Mark udp ipv6 as supporting msghdr::ubuf_info. In the original commit SOCK_SUPPORT_ZC was supposed to be set by a udp_init_sock() call from udp6_init_sock(), but d38afeec26ed4 ("tcp/udp: Call inet6_destroy_sock() in IPv6 ...") removed it and so ipv6 udp misses the flag. Cc: # 6.0 Fixes: e993ffe3da4bc ("net: flag sockets supporting msghdr originated zerocopy") Signed-off-by: Pavel Begunkov Signed-off-by: Jakub Kicinski --- net/ipv6/udp.c | 1 + 1 file changed, 1 insertion(+) (limited to 'net/ipv6/udp.c') diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 129ec5a9b0eb..bc65e5b7195b 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -66,6 +66,7 @@ int udpv6_init_sock(struct sock *sk) { skb_queue_head_init(&udp_sk(sk)->reader_queue); sk->sk_destruct = udpv6_destruct_sock; + set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags); return 0; } -- cgit v1.2.3-70-g09d2