FAILED: patch "[PATCH] vsock/virtio: reset connection on receiving queue overflow" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] vsock/virtio: reset connection on receiving queue overflow" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x a4f0b001782b21663d10df983b4b208195bec66c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026052841-mobility-surgery-8063@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a4f0b001782b21663d10df983b4b208195bec66c Mon Sep 17 00:00:00 2001
From: Stefano Garzarella <sgarzare@redhat.com>
Date: Mon, 18 May 2026 11:06:55 +0200
Subject: [PATCH] vsock/virtio: reset connection on receiving queue overflow

When there is no more space to queue an incoming packet, the packet is
silently dropped. This causes data loss without any notification to
either peer, since there is no retransmission.

Under normal circumstances, this should never happen. However, it could
happen if the other peer doesn't respect the credit, or if the skb
overhead, which we recently began to take into account with commit
059b7dbd20a6 ("vsock/virtio: fix potential unbounded skb queue"),
is too high.

Fix this by resetting the connection and setting the local socket error
to ENOBUFS when virtio_transport_recv_enqueue() can no longer queue a
packet, so both peers are explicitly notified of the failure rather than
silently losing data.

Fixes: ae6fcfbf5f03 ("vsock/virtio: discard packets if credit is not respected")
Cc: stable@vger.kernel.org
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20260518090656.134588-2-sgarzare@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 1e3409d28164..5028ff534888 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1335,7 +1335,7 @@ virtio_transport_recv_connecting(struct sock *sk,
 	return err;
 }
 
-static void
+static bool
 virtio_transport_recv_enqueue(struct vsock_sock *vsk,
 			      struct sk_buff *skb)
 {
@@ -1350,10 +1350,8 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk,
 	spin_lock_bh(&vvs->rx_lock);
 
 	can_enqueue = virtio_transport_inc_rx_pkt(vvs, len);
-	if (!can_enqueue) {
-		free_pkt = true;
+	if (!can_enqueue)
 		goto out;
-	}
 
 	if (le32_to_cpu(hdr->flags) & VIRTIO_VSOCK_SEQ_EOM)
 		vvs->msg_count++;
@@ -1393,6 +1391,8 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk,
 	spin_unlock_bh(&vvs->rx_lock);
 	if (free_pkt)
 		kfree_skb(skb);
+
+	return can_enqueue;
 }
 
 static int
@@ -1405,7 +1405,17 @@ virtio_transport_recv_connected(struct sock *sk,
 
 	switch (le16_to_cpu(hdr->op)) {
 	case VIRTIO_VSOCK_OP_RW:
-		virtio_transport_recv_enqueue(vsk, skb);
+		if (!virtio_transport_recv_enqueue(vsk, skb)) {
+			/* There is no more space to queue the packet, so let's
+			 * close the connection; otherwise, we'll lose data.
+			 */
+			(void)virtio_transport_reset(vsk, skb);
+			virtio_transport_do_close(vsk, true);
+			sk->sk_err = ENOBUFS;
+			sk_error_report(sk);
+			vsock_remove_sock(vsk);
+			break;
+		}
 		vsock_data_ready(sk);
 		return err;
 	case VIRTIO_VSOCK_OP_CREDIT_REQUEST: