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

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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: b1308dc015 ("[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>
This commit is contained in:
Hangyu Hua 2022-07-29 19:00:27 +08:00 committed by Jakub Kicinski
parent 1e02fd7671
commit a41b17ff9d
1 changed files with 5 additions and 5 deletions
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10
net/dccp/proto.c
View File

@ -736,11 +736,6 @@ 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);
/*
@ -759,6 +754,11 @@ 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;