virtio_net: fix missing lock protection on control_buf access

Refactored the handling of control_buf to be within the cvq_lock
critical section, mitigating race conditions between reading device
responses and new command submissions.

Fixes: 6f45ab3 ("virtio_net: Add a lock for the command VQ.")
Signed-off-by: Heng Qi <[email protected]>
Reviewed-by: Hariprasad Kelam <[email protected]>
Acked-by: Jason Wang <[email protected]>
Reviewed-by: Xuan Zhuo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Heng Qi

drivers/net/virtio_net.c

@@ -2686,6 +2686,7 @@ static bool virtnet_send_command_reply(struct virtnet_info *vi, u8 class, u8 cmd
 {
 	struct scatterlist *sgs[5], hdr, stat;
 	u32 out_num = 0, tmp, in_num = 0;
+	bool ok;
 	int ret;
 
 	/* Caller should know better */
@@ -2731,8 +2732,9 @@ static bool virtnet_send_command_reply(struct virtnet_info *vi, u8 class, u8 cmd
 	}
 
 unlock:
+	ok = vi->ctrl->status == VIRTIO_NET_OK;
 	mutex_unlock(&vi->cvq_lock);
-	return vi->ctrl->status == VIRTIO_NET_OK;
+	return ok;
 }
 
 static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,