Commit c1ba3c0c authored Jul 11, 2025 by Yun Lu Committed by David S. Miller Jul 13, 2025

af_packet: fix the SO_SNDTIMEO constraint not effective on tpacked_snd()



Due to the changes in commit 581073f6 ("af_packet: do not call
packet_read_pending() from tpacket_destruct_skb()"), every time
tpacket_destruct_skb() is executed, the skb_completion is marked as
completed. When wait_for_completion_interruptible_timeout() returns
completed, the pending_refcnt has not yet been reduced to zero.
Therefore, when ph is NULL, the wait function may need to be called
multiple times until packet_read_pending() finally returns zero.

We should call sock_sndtimeo() only once, otherwise the SO_SNDTIMEO
constraint could be way off.

Fixes: 581073f6 ("af_packet: do not call packet_read_pending() from tpacket_destruct_skb()")
Cc: stable@kernel.org
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Yun Lu <luyun@kylinos.cn>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 5e28d5a3

net/packet/af_packet.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -2785,7 +2785,7 @@ static int tpacket_snd(struct packet_sock po, struct msghdr msg)
		int len_sum = 0;
		int status = TP_STATUS_AVAILABLE;
		int hlen, tlen, copylen = 0;
		long timeo = 0;
		long timeo;

		mutex_lock(&po->pg_vec_lock);

		@@ -2839,6 +2839,7 @@ static int tpacket_snd(struct packet_sock po, struct msghdr msg)
		if ((size_max > dev->mtu + reserve + VLAN_HLEN) && !vnet_hdr_sz)
		size_max = dev->mtu + reserve + VLAN_HLEN;

		timeo = sock_sndtimeo(&po->sk, msg->msg_flags & MSG_DONTWAIT);
		reinit_completion(&po->skb_completion);

		do {
		@@ -2846,7 +2847,6 @@ static int tpacket_snd(struct packet_sock po, struct msghdr msg)
		TP_STATUS_SEND_REQUEST);
		if (unlikely(ph == NULL)) {
		if (need_wait && skb) {
		timeo = sock_sndtimeo(&po->sk, msg->msg_flags & MSG_DONTWAIT);
		timeo = wait_for_completion_interruptible_timeout(&po->skb_completion, timeo);
		if (timeo <= 0) {
		err = !timeo ? -ETIMEDOUT : -ERESTARTSYS;