Re: [syzbot] [kvm?] [net?] [virt?] WARNING in virtio_transport_send_pkt_info (2)

[Edward Adam Davis]

#syz test

diff --git a/net/core/datagram.c b/net/core/datagram.c
index c285c6465923..da10465cd8a4 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -748,10 +748,13 @@ int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
 			    size_t length,
 			    struct net_devmem_dmabuf_binding *binding)
 {
+	struct iov_iter_state state;
 	unsigned long orig_size = skb->truesize;
 	unsigned long truesize;
 	int ret;
 
+	iov_iter_save_state(from, &state);
+
 	if (msg && msg->msg_ubuf && msg->sg_from_iter)
 		ret = msg->sg_from_iter(skb, from, length);
 	else if (binding)
@@ -759,6 +762,9 @@ int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
 	else
 		ret = zerocopy_fill_skb_from_iter(skb, from, length);
 
+	if (ret)
+		iov_iter_restore(from, &state);
+
 	truesize = skb->truesize - orig_size;
 	if (sk && sk->sk_type == SOCK_STREAM) {
 		sk_wmem_queued_add(sk, truesize);