The xtables packet traverser performs an unconditional local_bh_disable(),
but the nf_tables evaluation loop does not.

Functions that are called from either xtables or nftables must assume
that they can be called in process context.

inet_twsk_deschedule_put() assumes that no softirq interrupt can occur.
If tproxy is used from nf_tables its possible that we'll deadlock
trying to aquire a lock already held in process context.

Add a small helper that takes care of this and use it.

Link: https://lore.kernel.org/netfilter-devel/401bd6ed-314a-a196-1cdc-e13c720cc8f2@balasys.hu/
Fixes: 4ed8eb6570a4 ("netfilter: nf_tables: Add native tproxy support")
Reported-and-tested-by: Major Dávid <major.david@balasys.hu>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Pablo Neira Ayuso says:

====================
Netfilter fixes for net

1) Fix broken listing of set elements when table has an owner.

2) Fix conntrack refcount leak in ctnetlink with related conntrack
   entries, from Hangyu Hua.

3) Fix use-after-free/double-free in ctnetlink conntrack insert path,
   from Florian Westphal.

4) Fix ip6t_rpfilter with VRF, from Phil Sutter.

5) Fix use-after-free in ebtables reported by syzbot, also from Florian.

6) Use skb->len in xt_length to deal with IPv6 jumbo packets,
   from Xin Long.

7) Fix NETLINK_LISTEN_ALL_NSID with ctnetlink, from Florian Westphal.

8) Fix memleak in {ip_,ip6_,arp_}tables in ENOMEM error case,
   from Pavel Tikhomirov.

* git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf:
  netfilter: x_tables: fix percpu counter block leak on error path when creating new netns
  netfilter: ctnetlink: make event listener tracking global
  netfilter: xt_length: use skb len to match in length_mt6
  netfilter: ebtables: fix table blob use-after-free
  netfilter: ip6t_rpfilter: Fix regression with VRF interfaces
  netfilter: conntrack: fix rmmod double-free race
  netfilter: ctnetlink: fix possible refcount leak in ctnetlink_create_conntrack()
  netfilter: nf_tables: allow to fetch set elements when table has an owner
====================

Link: https://lore.kernel.org/r/20230222092137.88637-1-pablo@netfilter.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Here is the stack where we allocate percpu counter block:

  +-< __alloc_percpu
    +-< xt_percpu_counter_alloc
      +-< find_check_entry # {arp,ip,ip6}_tables.c
        +-< translate_table

And it can be leaked on this code path:

  +-> ip6t_register_table
    +-> translate_table # allocates percpu counter block
    +-> xt_register_table # fails

there is no freeing of the counter block on xt_register_table fail.
Note: xt_percpu_counter_free should be called to free it like we do in
do_replace through cleanup_entry helper (or in __ip6t_unregister_table).

Probability of hitting this error path is low AFAICS (xt_register_table
can only return ENOMEM here, as it is not replacing anything, as we are
creating new netns, and it is hard to imagine that all previous
allocations succeeded and after that one in xt_register_table failed).
But it's worth fixing even the rare leak.

Fixes: 71ae0dff02d7 ("netfilter: xtables: use percpu rule counters")
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

We are not allowed to return an error at this point.
Looking at the code it looks like ret is always 0 at this
point, but its not.

t = find_table_lock(net, repl->name, &ret, &ebt_mutex);

... this can return a valid table, with ret != 0.

This bug causes update of table->private with the new
blob, but then frees the blob right away in the caller.

Syzbot report:

BUG: KASAN: vmalloc-out-of-bounds in __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168
Read of size 4 at addr ffffc90005425000 by task kworker/u4:4/74
Workqueue: netns cleanup_net
Call Trace:
 kasan_report+0xbf/0x1f0 mm/kasan/report.c:517
 __ebt_unregister_table+0xc00/0xcd0 net/bridge/netfilter/ebtables.c:1168
 ebt_unregister_table+0x35/0x40 net/bridge/netfilter/ebtables.c:1372
 ops_exit_list+0xb0/0x170 net/core/net_namespace.c:169
 cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613
...

ip(6)tables appears to be ok (ret should be 0 at this point) but make
this more obvious.

Fixes: c58dd2dd443c ("netfilter: Can't fail and free after table replacement")
Reported-by: syzbot+f61594de72d6705aea03@syzkaller.appspotmail.com
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

When calling ip6_route_lookup() for the packet arriving on the VRF
interface, the result is always the real (slave) interface. Expect this
when validating the result.

Fixes: acc641ab95b66 ("netfilter: rpfilter/fib: Populate flowic_l3mdev field")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

iptables/nftables support responding to tcp packets with tcp resets.

The generated tcp reset packet passes through both output and postrouting
netfilter hooks, but conntrack will never see them because the generated
skb has its ->nfct pointer copied over from the packet that triggered the
reset rule.

If the reset rule is used for established connections, this
may result in the conntrack entry to be around for a very long
time (default timeout is 5 days).

One way to avoid this would be to not copy the nf_conn pointer
so that the rest packet passes through conntrack too.

Problem is that output rules might not have the same conntrack
zone setup as the prerouting ones, so its possible that the
reset skb won't find the correct entry.  Generating a template
entry for the skb seems error prone as well.

Add an explicit "closing" function that switches a confirmed
conntrack entry to closed state and wire this up for tcp.

If the entry isn't confirmed, no action is needed because
the conntrack entry will never be committed to the table.

Reported-by: Russel King <linux@armlinux.org.uk>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Add a 'reset' flag just like with nft_object_ops::dump. This will be
useful to reset "anonymous stateful objects", e.g. simple rule counters.

No functional change intended.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

This is used to track when a duplicate segment received by various
reassembly units is dropped.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Currently netfilter's rpfilter and fib modules implicitely initialise
->flowic_uid with 0. This is normally the root UID. However, this isn't
the case in user namespaces, where user ID 0 is mapped to a different
kernel UID. By initialising ->flowic_uid with sock_net_uid(), we get
the root UID of the user namespace, thus keeping the same behaviour
whether or not we're running in a user namepspace.

Note, this is similar to commit 8bcfd0925ef1 ("ipv4: add missing
initialization for flowi4_uid"), which fixed the rp_filter sysctl.

Fixes: 622ec2c9d524 ("net: core: add UID to flows, rules, and routes")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Use the introduced field for correct operation with VRF devices instead
of conditionally overwriting flowic_oif. This is a partial revert of
commit b575b24b8eee3 ("netfilter: Fix rpfilter dropping vrf packets by
mistake"), implementing a simpler solution.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>