Patch "vsock: Update rx_bytes on read_skb()" has been added to the 6.11-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    vsock: Update rx_bytes on read_skb()

to the 6.11-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     vsock-update-rx_bytes-on-read_skb.patch
and it can be found in the queue-6.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 48bde160caf2a1d38995095dc6cdfffa34aa3405
Author: Michal Luczaj <mhal@xxxxxxx>
Date:   Sun Oct 13 18:26:40 2024 +0200

    vsock: Update rx_bytes on read_skb()
    
    [ Upstream commit 3543152f2d330141d9394d28855cb90b860091d2 ]
    
    Make sure virtio_transport_inc_rx_pkt() and virtio_transport_dec_rx_pkt()
    calls are balanced (i.e. virtio_vsock_sock::rx_bytes doesn't lie) after
    vsock_transport::read_skb().
    
    While here, also inform the peer that we've freed up space and it has more
    credit.
    
    Failing to update rx_bytes after packet is dequeued leads to a warning on
    SOCK_STREAM recv():
    
    [  233.396654] rx_queue is empty, but rx_bytes is non-zero
    [  233.396702] WARNING: CPU: 11 PID: 40601 at net/vmw_vsock/virtio_transport_common.c:589
    
    Fixes: 634f1a7110b4 ("vsock: support sockmap")
    Suggested-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
    Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
    Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
    Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
    Link: https://lore.kernel.org/bpf/20241013-vsock-fixes-for-redir-v2-2-d6577bbfe742@xxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 16ff976a86e3e..0f67cb0c64702 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1672,6 +1672,7 @@ int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_acto
 {
 	struct virtio_vsock_sock *vvs = vsk->trans;
 	struct sock *sk = sk_vsock(vsk);
+	struct virtio_vsock_hdr *hdr;
 	struct sk_buff *skb;
 	int off = 0;
 	int err;
@@ -1681,10 +1682,16 @@ int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_acto
 	 * works for types other than dgrams.
 	 */
 	skb = __skb_recv_datagram(sk, &vvs->rx_queue, MSG_DONTWAIT, &off, &err);
+	if (!skb) {
+		spin_unlock_bh(&vvs->rx_lock);
+		return err;
+	}
+
+	hdr = virtio_vsock_hdr(skb);
+	virtio_transport_dec_rx_pkt(vvs, le32_to_cpu(hdr->len));
 	spin_unlock_bh(&vvs->rx_lock);
 
-	if (!skb)
-		return err;
+	virtio_transport_send_credit_update(vsk);
 
 	return recv_actor(sk, skb);
 }