[PATCH V2] net: Fix skb_under_panic oops in neigh_resolve_output

From: ramesh . nagappa
Date: Sat Oct 06 2012 - 01:10:37 EST


The retry loop in neigh_resolve_output() and neigh_connected_output()
call dev_hard_header() with out reseting the skb to network_header.
This causes the retry to fail with skb_under_panic. The fix is to
reset the network_header within the retry loop.

Signed-off-by: Ramesh Nagappa <ramesh.nagappa@xxxxxxxxxxxx>
Reviewed-by: Shawn Lu <shawn.lu@xxxxxxxxxxxx>
Reviewed-by: Robert Coulson <robert.coulson@xxxxxxxxxxxx>
Reviewed-by: Billie Alsup <billie.alsup@xxxxxxxxxxxx>
---
net/core/neighbour.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 117afaf..058bb1e 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1301,8 +1301,6 @@ int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb)
if (!dst)
goto discard;

- __skb_pull(skb, skb_network_offset(skb));
-
if (!neigh_event_send(neigh, skb)) {
int err;
struct net_device *dev = neigh->dev;
@@ -1312,6 +1310,7 @@ int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb)
neigh_hh_init(neigh, dst);

do {
+ __skb_pull(skb, skb_network_offset(skb));
seq = read_seqbegin(&neigh->ha_lock);
err = dev_hard_header(skb, dev, ntohs(skb->protocol),
neigh->ha, NULL, skb->len);
@@ -1342,9 +1341,8 @@ int neigh_connected_output(struct neighbour *neigh, struct sk_buff *skb)
unsigned int seq;
int err;

- __skb_pull(skb, skb_network_offset(skb));
-
do {
+ __skb_pull(skb, skb_network_offset(skb));
seq = read_seqbegin(&neigh->ha_lock);
err = dev_hard_header(skb, dev, ntohs(skb->protocol),
neigh->ha, NULL, skb->len);
--
1.7.11.4

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