batman-adv: Fix NULL pointer dereference in DAT hash collision avoidance
An entry in DAT with the hashed position of 0 can cause a NULL pointer
dereference when the first entry is checked by batadv_choose_next_candidate.
This first candidate automatically has the max value of 0 and the max_orig_node
of NULL. Not checking max_orig_node for NULL in batadv_is_orig_node_eligible
will lead to a NULL pointer dereference when checking for the lowest address.
This problem was added in 785ea1144182c341b8b85b0f8180291839d176a8
("batman-adv: Distributed ARP Table - create DHT helper functions").
Signed-off-by: Pau Koning <paukoning@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 183f97a..5539215 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -440,7 +440,7 @@
/* this is an hash collision with the temporary selected node. Choose
* the one with the lowest address
*/
- if ((tmp_max == max) &&
+ if ((tmp_max == max) && max_orig_node &&
(batadv_compare_eth(candidate->orig, max_orig_node->orig) > 0))
goto out;