Commit 68a3765c authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso

netfilter: nf_tables: skip netdev events generated on netns removal

syzbot reported following (harmless) WARN:

 WARNING: CPU: 1 PID: 2648 at net/netfilter/core.c:468
  nft_netdev_unregister_hooks net/netfilter/nf_tables_api.c:230 [inline]
  nf_tables_unregister_hook include/net/netfilter/nf_tables.h:1090 [inline]
  __nft_release_basechain+0x138/0x640 net/netfilter/nf_tables_api.c:9524
  nft_netdev_event net/netfilter/nft_chain_filter.c:351 [inline]
  nf_tables_netdev_event+0x521/0x8a0 net/netfilter/nft_chain_filter.c:382

reproducer:
unshare -n bash -c 'ip link add br0 type bridge; nft add table netdev t ; \
 nft add chain netdev t ingress \{ type filter hook ingress device "br0" \
 priority 0\; policy drop\; \}'

Problem is that when netns device exit hooks create the UNREGISTER
event, the .pre_exit hook for nf_tables core has already removed the
base hook.  Notifier attempts to do this again.

The need to do base hook unregister unconditionally was needed in the past,
because notifier was last stage where reg->dev dereference was safe.

Now that nf_tables does the hook removal in .pre_exit, this isn't
needed anymore.

Reported-and-tested-by: syzbot+154bd5be532a63aa778b@syzkaller.appspotmail.com
Fixes: 767d1216 ("netfilter: nftables: fix possible UAF over chains from packet path in netns")
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 77076934
...@@ -342,12 +342,6 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev, ...@@ -342,12 +342,6 @@ static void nft_netdev_event(unsigned long event, struct net_device *dev,
return; return;
} }
/* UNREGISTER events are also happening on netns exit.
*
* Although nf_tables core releases all tables/chains, only this event
* handler provides guarantee that hook->ops.dev is still accessible,
* so we cannot skip exiting net namespaces.
*/
__nft_release_basechain(ctx); __nft_release_basechain(ctx);
} }
...@@ -366,6 +360,9 @@ static int nf_tables_netdev_event(struct notifier_block *this, ...@@ -366,6 +360,9 @@ static int nf_tables_netdev_event(struct notifier_block *this,
event != NETDEV_CHANGENAME) event != NETDEV_CHANGENAME)
return NOTIFY_DONE; return NOTIFY_DONE;
if (!check_net(ctx.net))
return NOTIFY_DONE;
nft_net = nft_pernet(ctx.net); nft_net = nft_pernet(ctx.net);
mutex_lock(&nft_net->commit_mutex); mutex_lock(&nft_net->commit_mutex);
list_for_each_entry(table, &nft_net->tables, list) { list_for_each_entry(table, &nft_net->tables, list) {
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment