linux/net/ipv4/netfilter, branch master

netfilter: x_tables: close dangling table module init race

2026-05-07T23:30:17Z

Similar to the previous ebtables patch: template add exposes the table to userspace, we must do this last to rnsure the pernet ops are set up (contain the destructors). Fixes: fdacd57c79b7 ("netfilter: x_tables: never register tables by default") Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: x_tables: add and use xtables_unregister_table_exit

2026-05-07T23:30:16Z

Previous change added xtables_unregister_table_pre_exit to detach the table from the packetpath and to unlink it from the active table list. In case of rmmod, userspace that is doing set/getsockopt for this table will not be able to re-instantiate the table: 1. The larval table has been removed already 2. existing instantiated table is no longer on the xt pernet table list. This adds the second stage helper: unlink the table from the dying list, free the hook ops (if any) and do the audit notification. It replaces xt_unregister_table(). Fixes: fdacd57c79b7 ("netfilter: x_tables: never register tables by default") Reported-by: Tristan Madani Reviewed-by: Tristan Madani Closes: https://lore.kernel.org/netfilter-devel/20260429175613.1459342-1-tristmd@gmail.com/ Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: x_tables: unregister the templates first

2026-05-07T23:30:16Z

When the module is going away we need to zap the template first. Else there is a small race window where userspace could instantiate a new table after the pernet exit function has removed the current table. Fixes: fdacd57c79b7 ("netfilter: x_tables: never register tables by default") Reported-by: Tristan Madani Reviewed-by: Tristan Madani Closes: https://lore.kernel.org/netfilter-devel/20260429175613.1459342-1-tristmd@gmail.com/ Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: x_tables: add and use xt_unregister_table_pre_exit

2026-05-07T23:30:16Z

Remove the copypasted variants of _pre_exit and add one single function in the xtables core. ebtables is not compatible with x_tables and therefore unchanged. This is a preparation patch to reduce noise in the followup bug fixes. Reviewed-by: Tristan Madani Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: x_tables: allocate hook ops while under mutex

2026-05-07T23:30:16Z

arp/ip(6)t_register_table() add the table to the per-netns list via xt_register_table() before allocating the per-netns hook ops copy via kmemdup_array(). This leaves a window where the table is visible in the list with ops=NULL. If the pernet exit happens runs concurrently the pre_exit callback finds the table via xt_find_table() and passes the NULL ops pointer to nf_unregister_net_hooks(), causing a NULL dereference: general protection fault in nf_unregister_net_hooks+0xbc/0x150 RIP: nf_unregister_net_hooks (net/netfilter/core.c:613) Call Trace: ipt_unregister_table_pre_exit iptable_mangle_net_pre_exit ops_pre_exit_list cleanup_net Fix by moving the ops allocation into the xtables core so the table is never in the list without valid ops. Also ensure the table is no longer processing packets before its torn down on error unwind. nf_register_net_hooks might have published at least one hook; call synchronize_rcu() if there was an error. audit log register message gets deferred until all operations have passed, this avoids need to emit another ureg message in case of error unwinding. Based on earlier patch by Tristan Madani. Fixes: f9006acc8dfe5 ("netfilter: arp_tables: pass table pointer via nf_hook_ops") Fixes: ee177a54413a ("netfilter: ip6_tables: pass table pointer via nf_hook_ops") Fixes: ae689334225f ("netfilter: ip_tables: pass table pointer via nf_hook_ops") Link: https://lore.kernel.org/netfilter-devel/20260429175613.1459342-1-tristmd@gmail.com/ Signed-off-by: Tristan Madani Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: nf_socket: skip socket lookup for non-first fragments

2026-04-30T15:59:01Z

Both nft_socket and xt_socket relies on L4 headers to perform socket lookup in the slow path. For fragmented packets, while the IP protocol remains constant across all fragments, only the first fragment contains the actual L4 header. As the expression/match could be attached to a chain with a priority lower than -400, it could bypass defragmentation. Add a check for fragmentation in the lookup functions directly so the problem is handled for both nft_socket and xt_socket at the same time. In addition, future users of the functions would not need to care about this. Fixes: 902d6a4c2a4f ("netfilter: nf_defrag: Skip defrag if NOTRACK is set") Fixes: 554ced0a6e29 ("netfilter: nf_tables: add support for native socket matching") Signed-off-by: Fernando Fernandez Mancera Signed-off-by: Pablo Neira Ayuso

netfilter: arp_tables: fix IEEE1394 ARP payload parsing

2026-04-21T10:44:39Z

Weiming Shi says: "arp_packet_match() unconditionally parses the ARP payload assuming two hardware addresses are present (source and target). However, IPv4-over-IEEE1394 ARP (RFC 2734) omits the target hardware address field, and arp_hdr_len() already accounts for this by returning a shorter length for ARPHRD_IEEE1394 devices. As a result, on IEEE1394 interfaces arp_packet_match() advances past a nonexistent target hardware address and reads the wrong bytes for both the target device address comparison and the target IP address. This causes arptables rules to match against garbage data, leading to incorrect filtering decisions: packets that should be accepted may be dropped and vice versa. The ARP stack in net/ipv4/arp.c (arp_create and arp_process) already handles this correctly by skipping the target hardware address for ARPHRD_IEEE1394. Apply the same pattern to arp_packet_match()." Mangle the original patch to always return 0 (no match) in case user matches on the target hardware address which is never present in IEEE1394. Note that this returns 0 (no match) for either normal and inverse match because matching in the target hardware address in ARPHRD_IEEE1394 has never been supported by arptables. This is intentional, matching on the target hardware address should never evaluate true for ARPHRD_IEEE1394. Moreover, adjust arpt_mangle to drop the packet too as AI suggests: In arpt_mangle, the logic assumes a standard ARP layout. Because IEEE1394 (FireWire) omits the target hardware address, the linear pointer arithmetic miscalculates the offset for the target IP address. This causes mangling operations to write to the wrong location, leading to packet corruption. To ensure safety, this patch drops packets (NF_DROP) when mangling is requested for these fields on IEEE1394 devices, as the current implementation cannot correctly map the FireWire ARP payload. This omits both mangling target hardware and IP address. Even if IP address mangling should be possible in IEEE1394, this would require to adjust arpt_mangle offset calculation, which has never been supported. Based on patch from Weiming Shi . Fixes: 6752c8db8e0c ("firewire net, ipv4 arp: Extend hardware address and remove driver-level packet inspection.") Reported-by: Xiang Mei Signed-off-by: Pablo Neira Ayuso

netfilter: nat: use kfree_rcu to release ops

2026-04-20T21:45:41Z

Florian Westphal says: "Historically this is not an issue, even for normal base hooks: the data path doesn't use the original nf_hook_ops that are used to register the callbacks. However, in v5.14 I added the ability to dump the active netfilter hooks from userspace. This code will peek back into the nf_hook_ops that are available at the tail of the pointer-array blob used by the datapath. The nat hooks are special, because they are called indirectly from the central nat dispatcher hook. They are currently invisible to the nfnl hook dump subsystem though. But once that changes the nat ops structures have to be deferred too." Update nf_nat_register_fn() to deal with partial exposition of the hooks from error path which can be also an issue for nfnetlink_hook. Fixes: e2cf17d3774c ("netfilter: add new hook nfnl subsystem") Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: remove register tracking infrastructure

2026-02-26T03:36:26Z

This facility was disabled in commit 9e539c5b6d9c ("netfilter: nf_tables: disable expression reduction infra"), because not all nft_exprs guarantee they will update the destination register: some may set NFT_BREAK instead to cancel evaluation of the rule. This has been dead code ever since. There are no plans to salvage this at this time, so remove this. Signed-off-by: Florian Westphal Link: https://patch.msgid.link/20260224205048.4718-10-fw@strlen.de Signed-off-by: Jakub Kicinski

ipv4: use dst4_mtu() instead of dst_mtu()

2026-02-03T01:49:29Z

When we expect an IPv4 dst, use dst4_mtu() instead of dst_mtu() to save some code space. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260130210303.3888261-8-edumazet@google.com Signed-off-by: Jakub Kicinski