vsock/loopback: use only sk_buff_head.lock to protect the packet queue

pkt_list_lock was used before commit 71dc9ec9ac7d ("virtio/vsock:
replace virtio_vsock_pkt with sk_buff") to protect the packet queue.
After that commit we switched to sk_buff and we are using
sk_buff_head.lock in almost every place to protect the packet queue
except in vsock_loopback_work() when we call skb_queue_splice_init().

As reported by syzbot, this caused unlocked concurrent access to the
packet queue between vsock_loopback_work() and
vsock_loopback_cancel_pkt() since it is not holding pkt_list_lock.

With the introduction of sk_buff_head, pkt_list_lock is redundant and
can cause confusion, so let's remove it and use sk_buff_head.lock
everywhere to protect the packet queue access.

Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
Cc: bobby.eshleman@bytedance.com
Reported-and-tested-by: syzbot+befff0a9536049e7902e@syzkaller.appspotmail.com
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
Reviewed-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
index 671e032..89905c0 100644 (file)
--- a/net/vmw_vsock/vsock_loopback.c
+++ b/net/vmw_vsock/vsock_loopback.c
@@ -15,7 +15,6 @@
 struct vsock_loopback {
        struct workqueue_struct *workqueue;
 
-       spinlock_t pkt_list_lock; /* protects pkt_list */
        struct sk_buff_head pkt_queue;
        struct work_struct pkt_work;
 };
@@ -32,9 +31,7 @@ static int vsock_loopback_send_pkt(struct sk_buff *skb)
        struct vsock_loopback *vsock = &the_vsock_loopback;
        int len = skb->len;
 
-       spin_lock_bh(&vsock->pkt_list_lock);
        skb_queue_tail(&vsock->pkt_queue, skb);
-       spin_unlock_bh(&vsock->pkt_list_lock);
 
        queue_work(vsock->workqueue, &vsock->pkt_work);
 
@@ -113,9 +110,9 @@ static void vsock_loopback_work(struct work_struct *work)
 
        skb_queue_head_init(&pkts);
 
-       spin_lock_bh(&vsock->pkt_list_lock);
+       spin_lock_bh(&vsock->pkt_queue.lock);
        skb_queue_splice_init(&vsock->pkt_queue, &pkts);
-       spin_unlock_bh(&vsock->pkt_list_lock);
+       spin_unlock_bh(&vsock->pkt_queue.lock);
 
        while ((skb = __skb_dequeue(&pkts))) {
                virtio_transport_deliver_tap_pkt(skb);
@@ -132,7 +129,6 @@ static int __init vsock_loopback_init(void)
        if (!vsock->workqueue)
                return -ENOMEM;
 
-       spin_lock_init(&vsock->pkt_list_lock);
        skb_queue_head_init(&vsock->pkt_queue);
        INIT_WORK(&vsock->pkt_work, vsock_loopback_work);
 
@@ -156,9 +152,7 @@ static void __exit vsock_loopback_exit(void)
 
        flush_work(&vsock->pkt_work);
 
-       spin_lock_bh(&vsock->pkt_list_lock);
        virtio_vsock_skb_queue_purge(&vsock->pkt_queue);
-       spin_unlock_bh(&vsock->pkt_list_lock);
 
        destroy_workqueue(vsock->workqueue);
 }