[PATCH nf-next 0/2] fixes for recent nf_compact hooks

[PATCH nf-next 0/2] fixes for recent nf_compact hooks

[Aaron Conole]

Two possible error conditions were caught during an extended testing
session, and by a build robot.  These patches fix the two issues (a
missing handler when config is changed, and a potential NULL
dereference).

Aaron Conole (2):
  netfilter: Fix potential null pointer dereference
  nf_set_hooks_head: acommodate different kconfig

 net/netfilter/core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

-- 
2.5.5

[PATCH nf-next 1/2] netfilter: Fix potential null pointer dereference

[Aaron Conole]

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

Signed-off-by: Aaron Conole <aconole@bytheb.org>
---
 net/netfilter/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 360c63d..e58e420 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -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;
-- 
2.5.5

[PATCH nf-next 2/2] nf_set_hooks_head: acommodate different kconfig

[Aaron Conole]

When CONFIG_NETFILTER_INGRESS is unset (or no), we need to handle
the request for registration properly by dropping the hook.  This
releases the entry during the set.

Signed-off-by: Aaron Conole <aconole@bytheb.org>
---
 net/netfilter/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index e58e420..1d0a4c9 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -90,10 +90,14 @@ static void nf_set_hooks_head(struct net *net, const struct nf_hook_ops *reg,
 {
 	switch (reg->pf) {
 	case NFPROTO_NETDEV:
+#ifdef CONFIG_NETFILTER_INGRESS
 		/* We already checked in nf_register_net_hook() that this is
 		 * used from ingress.
 		 */
 		rcu_assign_pointer(reg->dev->nf_hooks_ingress, entry);
+#else
+		kfree(entry);
+#endif
 		break;
 	default:
 		rcu_assign_pointer(net->nf.hooks[reg->pf][reg->hooknum],
-- 
2.5.5

Re: [PATCH nf-next 2/2] nf_set_hooks_head: acommodate different kconfig

[Florian Westphal]

Aaron Conole <aconole@bytheb.org> wrote:
> When CONFIG_NETFILTER_INGRESS is unset (or no), we need to handle
> the request for registration properly by dropping the hook.  This
> releases the entry during the set.
> 
> Signed-off-by: Aaron Conole <aconole@bytheb.org>
> ---
>  net/netfilter/core.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/net/netfilter/core.c b/net/netfilter/core.c
> index e58e420..1d0a4c9 100644
> --- a/net/netfilter/core.c
> +++ b/net/netfilter/core.c
> @@ -90,10 +90,14 @@ static void nf_set_hooks_head(struct net *net, const struct nf_hook_ops *reg,
>  {
>  	switch (reg->pf) {
>  	case NFPROTO_NETDEV:
> +#ifdef CONFIG_NETFILTER_INGRESS
>  		/* We already checked in nf_register_net_hook() that this is
>  		 * used from ingress.
>  		 */
>  		rcu_assign_pointer(reg->dev->nf_hooks_ingress, entry);
> +#else
> +		kfree(entry);
> +#endif
>  		break;

This looks dodgy (its correct though).

I'd propose to add a test to nf_register_net_hook()
to bail with -EOPNOSTUPP instead of this "#else kfree()" if we get
NFPROTO_NETDEV pf with CONFIG_NETFILTER_INGRESS=n build instead.

Re: [PATCH nf-next 2/2] nf_set_hooks_head: acommodate different kconfig

[Aaron Conole]

Florian Westphal <fw@strlen.de> writes:

> Aaron Conole <aconole@bytheb.org> wrote:
>> When CONFIG_NETFILTER_INGRESS is unset (or no), we need to handle
>> the request for registration properly by dropping the hook.  This
>> releases the entry during the set.
>> 
>> Signed-off-by: Aaron Conole <aconole@bytheb.org>
>> ---
>>  net/netfilter/core.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>> 
>> diff --git a/net/netfilter/core.c b/net/netfilter/core.c
>> index e58e420..1d0a4c9 100644
>> --- a/net/netfilter/core.c
>> +++ b/net/netfilter/core.c
>> @@ -90,10 +90,14 @@ static void nf_set_hooks_head(struct net *net, const struct nf_hook_ops *reg,
>>  {
>>  	switch (reg->pf) {
>>  	case NFPROTO_NETDEV:
>> +#ifdef CONFIG_NETFILTER_INGRESS
>>  		/* We already checked in nf_register_net_hook() that this is
>>  		 * used from ingress.
>>  		 */
>>  		rcu_assign_pointer(reg->dev->nf_hooks_ingress, entry);
>> +#else
>> +		kfree(entry);
>> +#endif
>>  		break;
>
> This looks dodgy (its correct though).
>
> I'd propose to add a test to nf_register_net_hook()
> to bail with -EOPNOSTUPP instead of this "#else kfree()" if we get
> NFPROTO_NETDEV pf with CONFIG_NETFILTER_INGRESS=n build instead.

Okay, I'll spin a new version.

Thanks for the review, Florian!

-Aaron