[PATCH net-next v10 05/11] virtio: set skb owner of virtio_transport_reset_no_sock() reply

[Bobby Eshleman <bobbyeshleman@gmail.com>]

From: Bobby Eshleman <bobbyeshleman@meta.com>

Associate reply packets with the sending socket. When vsock must reply
with an RST packet and there exists a sending socket (e.g., for
loopback), setting the skb owner to the socket correctly handles
reference counting between the skb and sk (i.e., the sk stays alive
until the skb is freed).

This allows the net namespace to be used for socket lookups for the
duration of the reply skb's lifetime, preventing race conditions between
the namespace lifecycle and vsock socket search using the namespace
pointer.

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
Changes in v10:
- break this out into its own patch for easy revert (Stefano)
---
 net/vmw_vsock/virtio_transport_common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 168e7517a3f0..5bb498caa19e 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1181,6 +1181,12 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
 		.type = le16_to_cpu(hdr->type),
 		.reply = true,
 
+		/* Set sk owner to socket we are replying to (may be NULL for
+		 * non-loopback). This keeps a reference to the sock and
+		 * sock_net(sk) until the reply skb is freed.
+		 */
+		.vsk = vsock_sk(skb->sk),
+
 		/* net or net_mode are not defined here because we pass
 		 * net and net_mode directly to t->send_pkt(), instead of
 		 * relying on virtio_transport_send_pkt_info() to pass them to

-- 
2.47.3