Commit 5119e438 authored Sep 28, 2016 by Aaron Conole Committed by Pablo Neira Ayuso Sep 30, 2016

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: e3b37f11 ("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>

parent 80378384

net/netfilter/core.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -160,7 +160,7 @@ void nf_unregister_net_hook(struct net net, const struct nf_hook_ops reg)

		mutex_lock(&nf_hook_mutex);
		hooks_entry = nf_hook_entry_head(net, reg);
		if (hooks_entry->orig_ops == reg) {
		if (hooks_entry && hooks_entry->orig_ops == reg) {
		nf_set_hooks_head(net, reg,
		nf_entry_dereference(hooks_entry->next));
		goto unlock;

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