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Commit 4212fa80 authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
Browse files

tcp: Fix NEW_SYN_RECV handling in inet_twsk_purge() 

commit 1c4e97dd2d3c9a3e84f7e26346aa39bc426d3249 upstream.

inet_twsk_purge() uses rcu to find TIME_WAIT and NEW_SYN_RECV
objects to purge.

These objects use SLAB_TYPESAFE_BY_RCU semantic and need special
care. We need to use refcount_inc_not_zero(&sk->sk_refcnt).

Reuse the existing correct logic I wrote for TIME_WAIT,
because both structures have common locations for
sk_state, sk_family, and netns pointer.

If after the refcount_inc_not_zero() the object fields longer match
the keys, use sock_gen_put(sk) to release the refcount.

Then we can call inet_twsk_deschedule_put() for TIME_WAIT,
inet_csk_reqsk_queue_drop_and_put() for NEW_SYN_RECV sockets,
with BH disabled.

Then we need to restart the loop because we had drop rcu_read_lock().

Fixes: 740ea3c4a0b2 ("tcp: Clean up kernel listener's reqsk in inet_twsk_purge()")
Link: https://lore.kernel.org/netdev/CANn89iLvFuuihCtt9PME2uS1WJATnf5fKjDToa1WzVnRzHnPfg@mail.gmail.com/T/#u


Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240308200122.64357-2-kuniyu@amazon.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
[shaozhengchao: resolved conflicts in 5.10]
Signed-off-by: default avatarZhengchao Shao <shaozhengchao@huawei.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9f06ebd1

net/ipv4/inet_timewait_sock.c

+19 −22
Original line number Diff line number Diff line
@@ -253,12 +253,12 @@ void __inet_twsk_schedule(struct inet_timewait_sock *tw, int timeo, bool rearm) 
}

EXPORT_SYMBOL_GPL(__inet_twsk_schedule);



/* Remove all non full sockets (TIME_WAIT and NEW_SYN_RECV) for dead netns */

void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family)

{

	struct inet_timewait_sock *tw;

	struct sock *sk;

	struct hlist_nulls_node *node;

	unsigned int slot;

	struct sock *sk;



	for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {

		struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
@@ -267,38 +267,35 @@ void inet_twsk_purge(struct inet_hashinfo *hashinfo, int family) 
		rcu_read_lock();

restart:

		sk_nulls_for_each_rcu(sk, node, &head->chain) {

			if (sk->sk_state != TCP_TIME_WAIT) {

				/* A kernel listener socket might not hold refcnt for net,

				 * so reqsk_timer_handler() could be fired after net is

				 * freed.  Userspace listener and reqsk never exist here.

				 */

				if (unlikely(sk->sk_state == TCP_NEW_SYN_RECV &&

					     hashinfo->pernet)) {

					struct request_sock *req = inet_reqsk(sk);



					inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);

				}

			int state = inet_sk_state_load(sk);



			if ((1 << state) & ~(TCPF_TIME_WAIT |

					     TCPF_NEW_SYN_RECV))

				continue;

			}



			tw = inet_twsk(sk);

			if ((tw->tw_family != family) ||

				refcount_read(&twsk_net(tw)->count))

			if (sk->sk_family != family ||

			    refcount_read(&sock_net(sk)->count))

				continue;



			if (unlikely(!refcount_inc_not_zero(&tw->tw_refcnt)))

			if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))

				continue;



			if (unlikely((tw->tw_family != family) ||

				     refcount_read(&twsk_net(tw)->count))) {

				inet_twsk_put(tw);

			if (unlikely(sk->sk_family != family ||

				     refcount_read(&sock_net(sk)->count))) {

				sock_gen_put(sk);

				goto restart;

			}



			rcu_read_unlock();

			local_bh_disable();

			inet_twsk_deschedule_put(tw);

			if (state == TCP_TIME_WAIT) {

				inet_twsk_deschedule_put(inet_twsk(sk));

			} else {

				struct request_sock *req = inet_reqsk(sk);



				inet_csk_reqsk_queue_drop_and_put(req->rsk_listener,

								  req);

			}

			local_bh_enable();

			goto restart_rcu;

		}