linux.git/net/netfilter, branch master

netfilter: nf_tables: reject immediate NF_QUEUE verdict

2026-04-01T09:55:30+00:00

nft_queue is always used from userspace nftables to deliver the NF_QUEUE
verdict. Immediately emitting an NF_QUEUE verdict is never used by the
userspace nft tools, so reject immediate NF_QUEUE verdicts.

The arp family does not provide queue support, but such an immediate
verdict is still reachable. Globally reject NF_QUEUE immediate verdicts
to address this issue.

Fixes: f342de4e2f33 ("netfilter: nf_tables: reject QUEUE/DROP verdict parameters")
Signed-off-by: Pablo Neira Ayuso

netfilter: x_tables: restrict xt_check_match/xt_check_target extensions for NFPROTO_ARP

2026-04-01T09:55:29+00:00

Weiming Shi says:

xt_match and xt_target structs registered with NFPROTO_UNSPEC can be
loaded by any protocol family through nft_compat. When such a
match/target sets .hooks to restrict which hooks it may run on, the
bitmask uses NF_INET_* constants. This is only correct for families
whose hook layout matches NF_INET_*: IPv4, IPv6, INET, and bridge
all share the same five hooks (PRE_ROUTING ... POST_ROUTING).

ARP only has three hooks (IN=0, OUT=1, FORWARD=2) with different
semantics. Because NF_ARP_OUT == 1 == NF_INET_LOCAL_IN, the .hooks
validation silently passes for the wrong reasons, allowing matches to
run on ARP chains where the hook assumptions (e.g. state->in being
set on input hooks) do not hold. This leads to NULL pointer
dereferences; xt_devgroup is one concrete example:

 Oops: general protection fault, probably for non-canonical address 0xdffffc0000000044: 0000 [#1] SMP KASAN NOPTI
 KASAN: null-ptr-deref in range [0x0000000000000220-0x0000000000000227]
 RIP: 0010:devgroup_mt+0xff/0x350
 Call Trace:
  
  nft_match_eval (net/netfilter/nft_compat.c:407)
  nft_do_chain (net/netfilter/nf_tables_core.c:285)
  nft_do_chain_arp (net/netfilter/nft_chain_filter.c:61)
  nf_hook_slow (net/netfilter/core.c:623)
  arp_xmit (net/ipv4/arp.c:666)
  
 Kernel panic - not syncing: Fatal exception in interrupt

Fix it by restricting arptables to NFPROTO_ARP extensions only.
Note that arptables-legacy only supports:

- arpt_CLASSIFY
- arpt_mangle
- arpt_MARK

that provide explicit NFPROTO_ARP match/target declarations.

Fixes: 9291747f118d ("netfilter: xtables: add device group match")
Reported-by: Xiang Mei 
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

netfilter: ipset: drop logically empty buckets in mtype_del

2026-04-01T09:55:29+00:00

mtype_del() counts empty slots below n->pos in k, but it only drops the
bucket when both n->pos and k are zero. This misses buckets whose live
entries have all been removed while n->pos still points past deleted slots.

Treat a bucket as empty when all positions below n->pos are unused and
release it directly instead of shrinking it further.

Fixes: 8af1c6fbd923 ("netfilter: ipset: Fix forceadd evaluation path")
Cc: stable@vger.kernel.org
Reported-by: Juefei Pu 
Reported-by: Xin Liu 
Signed-off-by: Yifan Wu 
Co-developed-by: Yuan Tan 
Signed-off-by: Yuan Tan 
Reviewed-by: Phil Sutter 
Signed-off-by: Pablo Neira Ayuso

netfilter: ctnetlink: ignore explicit helper on new expectations

2026-04-01T09:55:29+00:00

Use the existing master conntrack helper, anything else is not really
supported and it just makes validation more complicated, so just ignore
what helper userspace suggests for this expectation.

This was uncovered when validating CTA_EXPECT_CLASS via different helper
provided by userspace than the existing master conntrack helper:

  BUG: KASAN: slab-out-of-bounds in nf_ct_expect_related_report+0x2479/0x27c0
  Read of size 4 at addr ffff8880043fe408 by task poc/102
  Call Trace:
   nf_ct_expect_related_report+0x2479/0x27c0
   ctnetlink_create_expect+0x22b/0x3b0
   ctnetlink_new_expect+0x4bd/0x5c0
   nfnetlink_rcv_msg+0x67a/0x950
   netlink_rcv_skb+0x120/0x350

Allowing to read kernel memory bytes off the expectation boundary.

CTA_EXPECT_HELP_NAME is still used to offer the helper name to userspace
via netlink dump.

Fixes: bd0779370588 ("netfilter: nfnetlink_queue: allow to attach expectations to conntracks")
Reported-by: Qi Tang 
Signed-off-by: Pablo Neira Ayuso

netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent

2026-04-01T09:55:29+00:00

ctnetlink_alloc_expect() allocates expectations from a non-zeroing
slab cache via nf_ct_expect_alloc().  When CTA_EXPECT_NAT is not
present in the netlink message, saved_addr and saved_proto are
never initialized.  Stale data from a previous slab occupant can
then be dumped to userspace by ctnetlink_exp_dump_expect(), which
checks these fields to decide whether to emit CTA_EXPECT_NAT.

The safe sibling nf_ct_expect_init(), used by the packet path,
explicitly zeroes these fields.

Zero saved_addr, saved_proto and dir in the else branch, guarded
by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when
NAT is enabled.

Confirmed by priming the expect slab with NAT-bearing expectations,
freeing them, creating a new expectation without CTA_EXPECT_NAT,
and observing that the ctnetlink dump emits a spurious
CTA_EXPECT_NAT containing stale data from the prior allocation.

Fixes: 076a0ca02644 ("netfilter: ctnetlink: add NAT support for expectations")
Reported-by: kernel test robot 
Signed-off-by: Qi Tang 
Signed-off-by: Pablo Neira Ayuso

netfilter: nf_conntrack_helper: pass helper to expect cleanup

2026-04-01T09:55:29+00:00

nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy()
to remove expectations belonging to the helper being unregistered.
However, it passes NULL instead of the helper pointer as the data
argument, so expect_iter_me() never matches any expectation and all
of them survive the cleanup.

After unregister returns, nfnl_cthelper_del() frees the helper
object immediately.  Subsequent expectation dumps or packet-driven
init_conntrack() calls then dereference the freed exp->helper,
causing a use-after-free.

Pass the actual helper pointer so expectations referencing it are
properly destroyed before the helper object is freed.

  BUG: KASAN: slab-use-after-free in string+0x38f/0x430
  Read of size 1 at addr ffff888003b14d20 by task poc/103
  Call Trace:
   string+0x38f/0x430
   vsnprintf+0x3cc/0x1170
   seq_printf+0x17a/0x240
   exp_seq_show+0x2e5/0x560
   seq_read_iter+0x419/0x1280
   proc_reg_read+0x1ac/0x270
   vfs_read+0x179/0x930
   ksys_read+0xef/0x1c0
  Freed by task 103:
  The buggy address is located 32 bytes inside of
   freed 192-byte region [ffff888003b14d00, ffff888003b14dc0)

Fixes: ac7b84839003 ("netfilter: expect: add and use nf_ct_expect_iterate helpers")
Signed-off-by: Qi Tang 
Reviewed-by: Phil Sutter 
Signed-off-by: Pablo Neira Ayuso

netfilter: ipset: use nla_strcmp for IPSET_ATTR_NAME attr

2026-04-01T09:55:29+00:00

IPSET_ATTR_NAME and IPSET_ATTR_NAMEREF are of NLA_STRING type, they
cannot be treated like a c-string.

They either have to be switched to NLA_NUL_STRING, or the compare
operations need to use the nla functions.

Fixes: f830837f0eed ("netfilter: ipset: list:set set type support")
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

netfilter: x_tables: ensure names are nul-terminated

2026-04-01T09:55:29+00:00

Reject names that lack a \0 character before feeding them
to functions that expect c-strings.

Fixes tag is the most recent commit that needs this change.

Fixes: c38c4597e4bf ("netfilter: implement xt_cgroup cgroup2 path match")
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

netfilter: nfnetlink_log: account for netlink header size

2026-04-01T09:55:29+00:00

This is a followup to an old bug fix: NLMSG_DONE needs to account
for the netlink header size, not just the attribute size.

This can result in a WARN splat + drop of the netlink message,
but other than this there are no ill effects.

Fixes: 9dfa1dfe4d5e ("netfilter: nf_log: account for size of NLMSG_DONE attribute")
Reported-by: Yiming Qian 
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

netfilter: flowtable: strictly check for maximum number of actions

2026-04-01T09:50:14+00:00

The maximum number of flowtable hardware offload actions in IPv6 is:

* ethernet mangling (4 payload actions, 2 for each ethernet address)
* SNAT (4 payload actions)
* DNAT (4 payload actions)
* Double VLAN (4 vlan actions, 2 for popping vlan, and 2 for pushing)
  for QinQ.
* Redirect (1 action)

Which makes 17, while the maximum is 16. But act_ct supports for tunnels
actions too. Note that payload action operates at 32-bit word level, so
mangling an IPv6 address takes 4 payload actions.

Update flow_action_entry_next() calls to check for the maximum number of
supported actions.

While at it, rise the maximum number of actions per flow from 16 to 24
so this works fine with IPv6 setups.

Fixes: c29f74e0df7a ("netfilter: nf_flow_table: hardware offload support")
Reported-by: Hyunwoo Kim 
Signed-off-by: Pablo Neira Ayuso