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Subject[PATCH 4.4 54/93] batman-adv: Avoid nullptr dereference in dat after vlan_insert_tag
Date
From: Sven Eckelmann <sven@narfation.org>

commit 60154a1e0495ffb8343a95cefe1e874634572fa8 upstream.

vlan_insert_tag can return NULL on errors. The distributed arp table code
therefore has to check the return value of vlan_insert_tag for NULL before
it can safely operate on this pointer.

Fixes: be1db4f6615b ("batman-adv: make the Distributed ARP Table vlan aware")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/batman-adv/distributed-arp-table.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -993,9 +993,12 @@ bool batadv_dat_snoop_outgoing_arp_reque
if (!skb_new)
goto out;

- if (vid & BATADV_VLAN_HAS_TAG)
+ if (vid & BATADV_VLAN_HAS_TAG) {
skb_new = vlan_insert_tag(skb_new, htons(ETH_P_8021Q),
vid & VLAN_VID_MASK);
+ if (!skb_new)
+ goto out;
+ }

skb_reset_mac_header(skb_new);
skb_new->protocol = eth_type_trans(skb_new,
@@ -1073,9 +1076,12 @@ bool batadv_dat_snoop_incoming_arp_reque
*/
skb_reset_mac_header(skb_new);

- if (vid & BATADV_VLAN_HAS_TAG)
+ if (vid & BATADV_VLAN_HAS_TAG) {
skb_new = vlan_insert_tag(skb_new, htons(ETH_P_8021Q),
vid & VLAN_VID_MASK);
+ if (!skb_new)
+ goto out;
+ }

/* To preserve backwards compatibility, the node has choose the outgoing
* format based on the incoming request packet type. The assumption is

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