[PATCH 4.9 099/103] xen/netback: Reset nr_frags before freeing skb

Greg Kroah-Hartman
2019-08-22T17:39:21Z

From: Ross Lagerwall <ross.lagerwall@citrix.com>

[ Upstream commit 3a0233ddec554b886298de2428edb5c50a20e694 ]

At this point nr_frags has been incremented but the frag does not yet
have a page assigned so freeing the skb results in a crash. Reset
nr_frags before freeing the skb to prevent this.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/xen-netback/netback.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -927,6 +927,7 @@ static void xenvif_tx_build_gops(struct
skb_shinfo(skb)->nr_frags = MAX_SKB_FRAGS;
nskb = xenvif_alloc_skb(0);
if (unlikely(nskb == NULL)) {
+ skb_shinfo(skb)->nr_frags = 0;
kfree_skb(skb);
xenvif_tx_err(queue, &txreq, extra_count, idx);
if (net_ratelimit())
@@ -942,6 +943,7 @@ static void xenvif_tx_build_gops(struct

if (xenvif_set_skb_gso(queue->vif, skb, gso)) {
/* Failure in xenvif_set_skb_gso is fatal. */
+ skb_shinfo(skb)->nr_frags = 0;
kfree_skb(skb);
kfree_skb(nskb);
break;