Re: [PATCH nf-next v3 1/2] netfilter: Fix potential null pointer dereference

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.