tree fb9d0cb7d6486870a61abde7274baf05111e3d76
parent 803783849fed11e38a30f31932c02c815520da70
author Aaron Conole <aconole@bytheb.org> 1475076914 -0400
committer Pablo Neira Ayuso <pablo@netfilter.org> 1475259326 +0200

netfilter: Fix potential null pointer dereference

It's possible for nf_hook_entry_head to return NULL.  If two
nf_unregister_net_hook calls happen simultaneously with a single hook
entry in the list, both will enter the nf_hook_mutex critical section.
The first will successfully delete the head, but the second will see
this NULL pointer and attempt to dereference.

This fix ensures that no null pointer dereference could occur when such
a condition happens.

Fixes: e3b37f11e6e4 ("netfilter: replace list_head with single linked list")
Signed-off-by: Aaron Conole <aconole@bytheb.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>