From: Jason Wang <jasowang@redhat.com>
Date: Wed, 2 May 2012 03:42:06 +0000 (+0800)
Subject: macvtap: zerocopy: set SKBTX_DEV_ZEROCOPY only when skb is built successfully
X-Git-Tag: v3.4.12~50
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=2b3c7134014a200279e7ed31716e528cd009dfb0;p=karo-tx-linux.git

macvtap: zerocopy: set SKBTX_DEV_ZEROCOPY only when skb is built successfully

commit 01d6657b388438def19c8baaea28e742b6ed32ec upstream.

Current the SKBTX_DEV_ZEROCOPY is set unconditionally after
zerocopy_sg_from_iovec(), this would lead NULL pointer when macvtap
fails to build zerocopy skb because destructor_arg was not
initialized. Solve this by set this flag after the skb were built
successfully.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 7cd750f4c6a0..b99c418d6b2b 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -716,10 +716,9 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
 	if (!skb)
 		goto err;
 
-	if (zerocopy) {
+	if (zerocopy)
 		err = zerocopy_sg_from_iovec(skb, iv, vnet_hdr_len, count);
-		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
-	} else
+	else
 		err = skb_copy_datagram_from_iovec(skb, 0, iv, vnet_hdr_len,
 						   len);
 	if (err)
@@ -738,8 +737,10 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
 	rcu_read_lock_bh();
 	vlan = rcu_dereference_bh(q->vlan);
 	/* copy skb_ubuf_info for callback when skb has no error */
-	if (zerocopy)
+	if (zerocopy) {
 		skb_shinfo(skb)->destructor_arg = m->msg_control;
+		skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+	}
 	if (vlan)
 		macvlan_start_xmit(skb, vlan->dev);
 	else