Commit 51fb8c2c authored Jul 29, 2022 by Hangyu Hua Committed by Greg Kroah-Hartman Aug 25, 2022

dccp: put dccp_qpolicy_full() and dccp_qpolicy_push() in the same lock



[ Upstream commit a41b17ff9dacd22f5f118ee53d82da0f3e52d5e3 ]

In the case of sk->dccps_qpolicy == DCCPQ_POLICY_PRIO, dccp_qpolicy_full
will drop a skb when qpolicy is full. And the lock in dccp_sendmsg is
released before sock_alloc_send_skb and then relocked after
sock_alloc_send_skb. The following conditions may lead dccp_qpolicy_push
to add skb to an already full sk_write_queue:

thread1--->lock
thread1--->dccp_qpolicy_full: queue is full. drop a skb
thread1--->unlock
thread2--->lock
thread2--->dccp_qpolicy_full: queue is not full. no need to drop.
thread2--->unlock
thread1--->lock
thread1--->dccp_qpolicy_push: add a skb. queue is full.
thread1--->unlock
thread2--->lock
thread2--->dccp_qpolicy_push: add a skb!
thread2--->unlock

Fix this by moving dccp_qpolicy_full.

Fixes: b1308dc0 ("[DCCP]: Set TX Queue Length Bounds via Sysctl")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Link: https://lore.kernel.org/r/20220729110027.40569-1-hbh25y@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent d3b29226

net/dccp/proto.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -765,11 +765,6 @@ int dccp_sendmsg(struct sock sk, struct msghdr msg, size_t len)

		lock_sock(sk);

		if (dccp_qpolicy_full(sk)) {
		rc = -EAGAIN;
		goto out_release;
		}

		timeo = sock_sndtimeo(sk, noblock);

		/*
		@@ -788,6 +783,11 @@ int dccp_sendmsg(struct sock sk, struct msghdr msg, size_t len)
		if (skb == NULL)
		goto out_release;

		if (dccp_qpolicy_full(sk)) {
		rc = -EAGAIN;
		goto out_discard;
		}

		if (sk->sk_state == DCCP_CLOSED) {
		rc = -ENOTCONN;
		goto out_discard;