[PATCH nf-next v3 0/2] fixes for recent nf_compact hooks

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

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.

Signed-off-by: Aaron Conole <redacted>
---
 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;

-- 
2.7.4

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 <redacted>
---
 net/netfilter/core.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index e58e420..61e8a9d 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c

@@ -90,10 +90,12 @@ 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);
+#endif
 		break;
 	default:
 		rcu_assign_pointer(net->nf.hooks[reg->pf][reg->hooknum],

@@ -107,10 +109,15 @@ int nf_register_net_hook(struct net *net, const struct nf_hook_ops *reg)
 	struct nf_hook_entry *hooks_entry;
 	struct nf_hook_entry *entry;
 
-	if (reg->pf == NFPROTO_NETDEV &&
-	    (reg->hooknum != NF_NETDEV_INGRESS ||
-	     !reg->dev || dev_net(reg->dev) != net))
-		return -EINVAL;
+	if (reg->pf == NFPROTO_NETDEV) {
+#ifndef CONFIG_NETFILTER_INGRESS
+		if (reg->hooknum == NF_NETDEV_INGRESS)
+			return -EOPNOTSUPP;
+#endif
+		if (reg->hooknum != NF_NETDEV_INGRESS ||
+		    !reg->dev || dev_net(reg->dev) != net)
+			return -EINVAL;
+	}
 
 	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 	if (!entry)

-- 
2.7.4

On Wed, 2016-09-28 at 09:12 -0400, Aaron Conole wrote:

When was the bug added exactly ?

For all bug fixes, you need to add a Fixes: tag.

Like :

Fixes: e3b37f11e6e4 ("netfilter: replace list_head with single linked list")

So that 100 different people in stable teams do not have to do the archeology themselves ...

Thanks.

Eric Dumazet [off-list ref] writes:

On Wed, 2016-09-28 at 09:12 -0400, Aaron Conole wrote:

quoted

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.

Signed-off-by: Aaron Conole <redacted>
---
 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;

When was the bug added exactly ?

Sunday, on the nf-next tree.

For all bug fixes, you need to add a Fixes: tag.

Like :

Fixes: e3b37f11e6e4 ("netfilter: replace list_head with single linked list")

I would but it's in nf-next tree, and I'm not sure how pulls go.  If
they are done via patch imports, then the sha sums will be wrong and the
commit message will be misleading.  If the sums are preserved, then I
can resubmit with this information.

So that 100 different people in stable teams do not have to do the
archeology themselves ...

Thanks.

Thanks for the review, Eric.

On Wed, 2016-09-28 at 10:56 -0400, Aaron Conole wrote:

Eric Dumazet [off-list ref] writes:

quoted

On Wed, 2016-09-28 at 09:12 -0400, Aaron Conole wrote:

quoted

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.

Signed-off-by: Aaron Conole <redacted>
---
 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;

When was the bug added exactly ?

Sunday, on the nf-next tree.

quoted

For all bug fixes, you need to add a Fixes: tag.

Like :

Fixes: e3b37f11e6e4 ("netfilter: replace list_head with single linked list")

I would but it's in nf-next tree, and I'm not sure how pulls go.  If
they are done via patch imports, then the sha sums will be wrong and the
commit message will be misleading.  If the sums are preserved, then I
can resubmit with this information.

I gave the (12 digits) sha-1 as present in David Miller net-next tree.

https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=e3b37f11e6e4e6b6f02cc762f182ce233d2c1c9d


This wont change, because David never rebases his tree under normal
operations.

Thanks.

Eric Dumazet [off-list ref] writes:

On Wed, 2016-09-28 at 10:56 -0400, Aaron Conole wrote:

quoted

Eric Dumazet [off-list ref] writes:

quoted

On Wed, 2016-09-28 at 09:12 -0400, Aaron Conole wrote:

quoted

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.

Signed-off-by: Aaron Conole <redacted>
---
 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;

When was the bug added exactly ?

Sunday, on the nf-next tree.

quoted

For all bug fixes, you need to add a Fixes: tag.

Like :

Fixes: e3b37f11e6e4 ("netfilter: replace list_head with single linked list")

I would but it's in nf-next tree, and I'm not sure how pulls go.  If
they are done via patch imports, then the sha sums will be wrong and the
commit message will be misleading.  If the sums are preserved, then I
can resubmit with this information.

I gave the (12 digits) sha-1 as present in David Miller net-next tree.

https://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=e3b37f11e6e4e6b6f02cc762f182ce233d2c1c9d


This wont change, because David never rebases his tree under normal
operations.

Thanks.

Thank you very much, Eric.  I've reposted.

-Aaron