[PATCH 3.15 076/109] xen-netback: Fix releasing frag_list skbs in error path

From: Greg Kroah-Hartman
Date: Sat Jul 26 2014 - 15:22:50 EST


3.15-stable review patch. If anyone has any objections, please let me know.

------------------

From: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>

[ Upstream commit b42cc6e421e7bf74e545483aa34b99d2a2ca6d3a ]

When the grant operations failed, the skb is freed up eventually, and it tries
to release the frags, if there is any. For the main skb nr_frags is set to 0 to
avoid this, but on the frag_list it iterates through the frags array, and tries
to call put_page on the page pointer which contains garbage at that time.

Signed-off-by: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
Reported-by: Armin Zentai <armin.zentai@xxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/xen-netback/netback.c | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1498,7 +1498,16 @@ static int xenvif_tx_submit(struct xenvi

/* Check the remap error code. */
if (unlikely(xenvif_tx_check_gop(vif, skb, &gop_map, &gop_copy))) {
+ /* If there was an error, xenvif_tx_check_gop is
+ * expected to release all the frags which were mapped,
+ * so kfree_skb shouldn't do it again
+ */
skb_shinfo(skb)->nr_frags = 0;
+ if (skb_has_frag_list(skb)) {
+ struct sk_buff *nskb =
+ skb_shinfo(skb)->frag_list;
+ skb_shinfo(nskb)->nr_frags = 0;
+ }
kfree_skb(skb);
continue;
}


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