[PATCH net 2/6] batman-adv: access unicast_ttvn skb->data only after skb realloc

[Simon Wunderlich <sw@simonwunderlich.de>]

From: Sven Eckelmann <sven@narfation.org>

The pskb_may_pull() called by batadv_get_vid() could reallocate the buffer
behind the skb. Variables which were pointing to the old buffer need to be
reassigned to avoid an use-after-free.

This was done correctly for the ethernet header but missed for the
unicast_packet pointer.

Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Fixes: c018ad3de61a ("batman-adv: add the VLAN ID attribute to the TT entry")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/routing.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index c05fcc9241add..2cc2307a41702 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -855,8 +855,8 @@ static bool batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
 	if (skb_cow(skb, sizeof(*unicast_packet)) < 0)
 		return false;
 
-	unicast_packet = (struct batadv_unicast_packet *)skb->data;
 	vid = batadv_get_vid(skb, hdr_len);
+	unicast_packet = (struct batadv_unicast_packet *)skb->data;
 	ethhdr = (struct ethhdr *)(skb->data + hdr_len);
 
 	/* do not reroute multicast frames in a unicast header */
-- 
2.47.3