syzbot reported following splat:
BUG: KASAN: use-after-free in __nf_ct_ext_exist
include/net/netfilter/nf_conntrack_extend.h:53 [inline]
BUG: KASAN: use-after-free in nf_ct_deliver_cached_events+0x5c3/0x6d0
net/netfilter/nf_conntrack_ecache.c:205
nf_conntrack_confirm include/net/netfilter/nf_conntrack_core.h:65 [inline]
nf_confirm+0x3d8/0x4d0 net/netfilter/nf_conntrack_proto.c:154
[..]

While there is no reproducer yet, the syzbot report contains one
interesting bit of information:

Freed by task 27585:
[..]
 kfree+0x10a/0x2c0 mm/slab.c:3757
 nf_ct_ext_destroy+0x2ab/0x2e0 net/netfilter/nf_conntrack_extend.c:38
 nf_conntrack_free+0x8f/0xe0 net/netfilter/nf_conntrack_core.c:1418
 destroy_conntrack+0x1a2/0x270 net/netfilter/nf_conntrack_core.c:626
 nf_conntrack_put include/linux/netfilter/nf_conntrack_common.h:31 [inline]
 nf_ct_resolve_clash net/netfilter/nf_conntrack_core.c:915 [inline]
 ^^^^^^^^^^^^^^^^^^^
 __nf_conntrack_confirm+0x21ca/0x2830 net/netfilter/nf_conntrack_core.c:1038
 nf_conntrack_confirm include/net/netfilter/nf_conntrack_core.h:63 [inline]
 nf_confirm+0x3e7/0x4d0 net/netfilter/nf_conntrack_proto.c:154

This is whats happening:

1. a conntrack entry is about to be confirmed (added to hash table).
2. a clash with existing entry is detected.
3. nf_ct_resolve_clash() puts skb->nfct (the "losing" entry).
4. this entry now has a refcount of 0 and is freed to SLAB_TYPESAFE_BY_RCU
   kmem cache.

skb->nfct has been replaced by the one found in the hash.
Problem is that nf_conntrack_confirm() uses the old ct:

static inline int nf_conntrack_confirm(struct sk_buff *skb)
{
 struct nf_conn *ct = (struct nf_conn *)skb_nfct(skb);
 int ret = NF_ACCEPT;

  if (ct) {
    if (!nf_ct_is_confirmed(ct))
       ret = __nf_conntrack_confirm(skb);
    if (likely(ret == NF_ACCEPT))
	nf_ct_deliver_cached_events(ct); /* This ct has refcount 0! */
  }
  return ret;
}

As of "netfilter: conntrack: free extension area immediately", we can't
access conntrack extensions in this case.

To fix this, make sure we check the dying bit presence before attempting
to get the eache extension.

Reported-by: syzbot+c7aabc9fe93e7f3637ba@syzkaller.appspotmail.com
Fixes: 2ad9d774 ("netfilter: conntrack: free extension area immediately")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

This patch allows you to register one netdev basechain to multiple
devices. This adds a new NFTA_HOOK_DEVS netlink attribute to specify
the list of netdevices. Basechains store a list of hooks.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

After unbinding the list of flow_block callbacks, iterate over it to
remove the existing rules in the netdevice that has just been
unregistered.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Add helper function to set up the flow_cls_offload object.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

This allows to reuse nft_setup_cb_call() from the callback unbind path.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Add nft_flow_block_chain() helper function to reuse this function from
netdev event handler.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Rise the maximum limit of devices per flowtable up to 256. Rename
NFT_FLOWTABLE_DEVICE_MAX to NFT_NETDEVICE_MAX in preparation to reuse
the netdev hook parser for ingress basechain.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Allow netdevice only once per flowtable, otherwise hit EEXIST.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Use a list of hooks per device instead an array.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Hardware offload needs access to the priority field, store this field in
the nf_flowtable object.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Signed-off-by: Norman Rasmussen <norman@rasmussen.co.za>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

At this time, NF_HOOK_LIST() macro will iterate the list and then calls
nf_hook() for each individual skb.

This makes it so the entire list is passed into the netfilter core.
The advantage is that we only need to fetch the rule blob once per list
instead of per-skb.

NF_HOOK_LIST now only works for ipv4 and ipv6, as those are the only
callers.

v2: use skb_list_del_init() instead of list_del (Edward Cree)
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Instead of waiting for rcu grace period just free it directly.

This is safe because conntrack lookup doesn't consider extensions.

Other accesses happen while ct->ext can't be free'd, either because
a ct refcount was taken or because the conntrack hash bucket lock or
the dying list spinlock have been taken.

This allows to remove __krealloc in a followup patch, netfilter was the
only user.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

When dumping the unconfirmed lists, the cpu that is processing the ct
entry can reallocate ct->ext at any time.

Right now accessing the extensions from another CPU is ok provided
we're holding rcu read lock: extension reallocation does use rcu.

Once RCU isn't used anymore this becomes unsafe, so skip extensions for
the unconfirmed list.

Dumping the extension area for confirmed or dying conntracks is fine:
no reallocations are allowed and list iteration holds appropriate
locks that prevent ct (and this ct->ext) from getting free'd.

v2: fix compiler warnings due to misue of 'const' and missing return
    statement (kbuild robot).
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Pablo Neira Ayuso says:

====================
IPVS updates for v5.5

1) Two patches to speedup ipvs netns dismantle, from Haishuang Yan.

2) Three patches to add selftest script for ipvs, also from
   Haishuang Yan.

3) Simplify __ip_vs_get_out_rt() from zhang kai.
====================
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Once ct->ext gets free'd via kfree() rather than kfree_rcu we can't
access the extension area anymore without owning the conntrack.

This is a special case:

The worker is walking the pcpu dying list while holding dying list lock:
Neither ct nor ct->ext can be free'd until after the walk has completed.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Test virtual server via ipip tunnel.

Tested:
# selftests: netfilter: ipvs.sh
# Testing DR mode...
# Testing NAT mode...
# Testing Tunnel mode...
# ipvs.sh: PASS
ok 6 selftests: netfilter: ipvs.sh
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

Test virtual server via NAT.

Tested:
# selftests: netfilter: ipvs.sh
# Testing DR mode...
# Testing NAT mode...
# ipvs.sh: PASS
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

Test virutal server via directing routing for IPv4.

Tested:

# selftests: netfilter: ipvs.sh
# Testing DR mode...
# ipvs.sh: PASS
ok 6 selftests: netfilter: ipvs.sh
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

It's better to batch __ip_vs_cleanup to speedup ipvs
devices dismantle.
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

It's better to batch __ip_vs_cleanup to speedup ipvs
connections dismantle.
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

In the end of function __ip_vs_get_out_rt/__ip_vs_get_out_rt_v6,the
'local' variable is always zero.
Signed-off-by: zhang kai <zhangkaiheb@126.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

ip_set_get_ip_port() is only used in ip_set_bitmap_port.c.  Move it
there and make it static.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

One inline function in ip_set_bitmap.h is only called in
ip_set_bitmap_ip.c: move it and remove inline function specifier.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

ip_set_put_flags is rather large for a static inline function in a
header-file.  Move it to ip_set_core.c and export it.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Several inline functions in ip_set.h are only called in ip_set_core.c:
move them and remove inline function specifier.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Most of the functions are only called from within ip_set_core.c.

The exception is ip_set_init_comment.  However, this is too complex to
be a good candidate for a static inline function.  Move it to
ip_set_core.c, change its linkage to extern and export it, leaving a
declaration in ip_set.h.

ip_set_comment_free is only used as an extension destructor, so change
its prototype to match and drop cast.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

The inline function-specifier should not be used for static functions
defined in .c files since it bloats the kernel.  Instead leave the
compiler to decide which functions to inline.

While a couple of the files affected (ip_set_*_gen.h) are technically
headers, they contain templates for generating the common parts of
particular set-types and so we treat them like .c files.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Use a local variable to hold comment in order to align the arguments of
ip_set_comment_free properly.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Jiri Pirko says:

====================
create netdevsim instances in namespace

Allow user to create netdevsim devlink and netdevice instances in a
network namespace according to the namespace where the user resides in.
Add a selftest to test this.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Add a test that creates netdevsim instance inside network namespace
and verifies that the related devlink instance and port netdevices
reside in the namespace.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When user does create new netdevsim instance using sysfs bus file,
create the devlink instance and related netdev instance in the namespace
of the caller.
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

For newly allocated devlink instance allow drivers to set net struct
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Jakub Kicinski says:

====================
net/tls: add ctrl path tracing and statistics

This set adds trace events related to TLS offload and basic MIB stats
for TLS.

First patch contains the TLS offload related trace points. Those are
helpful in troubleshooting offload issues, especially around the
resync paths.

Second patch adds a tracepoint to the fastpath of device offload,
it's separated out in case there will be objections to adding
fast path tracepoints. Again, it's quite useful for debugging
offload issues.

Next four patches add MIB statistics. The statistics are implemented
as per-cpu per-netns counters. Since there are currently no fast path
statistics we could move to atomic variables. Per-CPU seem more common.

Most basic statistics are number of created and live sessions, broken
out to offloaded and non-offloaded. Users seem to like those a lot.

Next there is a statistic for decryption errors. These are primarily
useful for device offload debug, in normal deployments decryption
errors should not be common.

Last but not least a counter for device RX resync.
====================
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add a statistic for number of RX resyncs sent down to the NIC.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add a statistic for TLS record decryption errors.

Since devices are supposed to pass records as-is when they
encounter errors this statistic will count bad records in
both pure software and inline crypto configurations.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add SNMP stats for number of sockets with successfully
installed sessions.  Break them down to software and
hardware ones.  Note that if hardware offload fails
stack uses software implementation, and counts the
session appropriately.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add a skeleton structure for adding TLS statistics.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add a tracepoint to the TLS offload's fast path. This tracepoint
can be used to track the decrypted and encrypted status of received
records. Records decrypted by the device should have decrypted set
to 1, records which have neither decrypted nor decrypted set are
partially decrypted, require re-encryption and therefore are most
expensive to deal with.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add tracing of device-related interaction to aid performance
analysis, especially around resync:

 tls:tls_device_offload_set
 tls:tls_device_rx_resync_send
 tls:tls_device_rx_resync_nh_schedule
 tls:tls_device_rx_resync_nh_delay
 tls:tls_device_tx_resync_req
 tls:tls_device_tx_resync_send
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>