[PATCH 3.19.y-ckt 28/40] vlan: pull on __vlan_insert_tag error path and fix csum correction

From: Kamal Mostafa
Date: Wed May 25 2016 - 13:36:51 EST

3.19.8-ckt22 -stable review patch. If anyone has any objections, please let me know.


From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>

[ Upstream commit 9241e2df4fbc648a92ea0752918e05c26255649e ]

When __vlan_insert_tag() fails from skb_vlan_push() path due to the
skb_cow_head(), we need to undo the __skb_push() in the error path
as well that was done earlier to move skb->data pointer to mac header.

Moreover, I noticed that when in the non-error path the __skb_pull()
is done and the original offset to mac header was non-zero, we fixup
from a wrong skb->data offset in the checksum complete processing.

So the skb_postpush_rcsum() really needs to be done before __skb_pull()
where skb->data still points to the mac header start and thus operates
under the same conditions as in __vlan_insert_tag().

Fixes: 93515d53b133 ("net: move vlan pop/push functions into common code")
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
net/core/skbuff.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b987b6c..9afbb1b 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4356,13 +4356,16 @@ int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
__skb_push(skb, offset);
err = __vlan_insert_tag(skb, skb->vlan_proto,
- if (err)
+ if (err) {
+ __skb_pull(skb, offset);
return err;
+ }
skb->protocol = skb->vlan_proto;
skb->mac_len += VLAN_HLEN;
- __skb_pull(skb, offset);

skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
+ __skb_pull(skb, offset);
__vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
return 0;