kernel/linux.git/net/netfilter, branch master

netfilter: skip recording stale or retransmitted INIT

2026-04-29T00:52:19+00:00

An INIT whose init_tag matches the peer's vtag does not provide new state information. It indicates either: - a stale INIT (after INIT-ACK has already been seen on the same side), or - a retransmitted INIT (after INIT has already been recorded on the same side). In both cases, the INIT must not update ct->proto.sctp.init[] state, since it does not advance the handshake tracking and may otherwise corrupt INIT/INIT-ACK validation logic. Allow INIT processing only when the conntrack entry is newly created (SCTP_CONNTRACK_NONE), or when the init_tag differs from the stored peer vtag. Note it skips the check for the ct with old_state SCTP_CONNTRACK_NONE in nf_conntrack_sctp_packet(), as it is just created in sctp_new() where it set ct->proto.sctp.vtag[IP_CT_DIR_REPLY] = ih->init_tag. Fixes: 9fb9cbb1082d ("[NETFILTER]: Add nf_conntrack subsystem.") Signed-off-by: Xin Long Reviewed-by: Marcelo Ricardo Leitner Acked-by: Florian Westphal Link: https://patch.msgid.link/ee56c3e416452b2a40589a2a85245ac2ad5e9f4b.1777214801.git.lucien.xin@gmail.com Signed-off-by: Jakub Kicinski

netfilter: nf_conntrack_sip: don't use simple_strtoul

2026-04-24T18:09:57+00:00

Replace unsafe port parsing in epaddr_len(), ct_sip_parse_header_uri(), and ct_sip_parse_request() with a new sip_parse_port() helper that validates each digit against the buffer limit, eliminating the use of simple_strtoul() which assumes NUL-terminated strings. The previous code dereferenced pointers without bounds checks after sip_parse_addr() and relied on simple_strtoul() on non-NUL-terminated skb data. A port that reaches the buffer limit without a trailing character is also rejected as malformed. Also get rid of all simple_strtoul() usage in conntrack, prefer a stricter version instead. There are intentional changes: - Bail out if number is > UINT_MAX and indicate a failure, same for too long sequences. While we do accept 05535 as port 5535, we will not accept e.g. 'sip:10.0.0.1:005060'. While its syntactically valid under RFC 3261, we should restrict this to not waste cycles when presented with malformed packets with 64k '0' characters. - Force base 10 in ct_sip_parse_numerical_param(). This is used to fetch 'expire=' and 'rports='; both are expected to use base-10. - In nf_nat_sip.c, only accept the parsed value if its within the 1k-64k range. - epaddr_len now returns 0 if the port is invalid, as it already does for invalid ip addresses. This is intentional. nf_conntrack_sip performs lots of guesswork to find the right parts of the message to parse. Being stricter could break existing setups. Connection tracking helpers are designed to allow traffic to pass, not to block it. Based on an earlier patch from Jenny Guanni Qu . Fixes: 05e3ced297fe ("[NETFILTER]: nf_conntrack_sip: introduce SIP-URI parsing helper") Reported-by: Klaudia Kloc Reported-by: Dawid Moczadło Reported-by: Jenny Guanni Qu . Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: reject zero shift in nft_bitwise

2026-04-24T18:09:57+00:00

Reject zero shift operands for nft_bitwise left and right shift expressions during initialization. The carry propagation logic computes the carry from the adjacent 32-bit word using BITS_PER_TYPE(u32) - shift. A zero shift operand turns this into a 32-bit shift, which is undefined behaviour. Reject zero shift operands in the control plane, alongside the existing check for values greater than or equal to 32, so malformed rules never reach the packet path. Fixes: 567d746b55bc ("netfilter: bitwise: add support for shifts.") Cc: stable@kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Kai Ma Signed-off-by: Ren Wei Reviewed-by: Fernando Fernandez Mancera Signed-off-by: Pablo Neira Ayuso

netfilter: xt_policy: fix strict mode inbound policy matching

2026-04-24T18:04:56+00:00

match_policy_in() walks sec_path entries from the last transform to the first one, but strict policy matching needs to consume info->pol[] in the same forward order as the rule layout. Derive the strict-match policy position from the number of transforms already consumed so that multi-element inbound rules are matched consistently. Fixes: c4b885139203 ("[NETFILTER]: x_tables: replace IPv4/IPv6 policy match by address family independant version") Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Jiexun Wang Signed-off-by: Ren Wei Acked-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: add hook transactions for device deletions

2026-04-21T10:48:44+00:00

Restore the flag that indicates that the hook is going away, ie. NFT_HOOK_REMOVE, but add a new transaction object to track deletion of hooks without altering the basechain/flowtable hook_list during the preparation phase. The existing approach that moves the hook from the basechain/flowtable hook_list to transaction hook_list breaks netlink dump path readers of this RCU-protected list. It should be possible use an array for nft_trans_hook to store the deleted hooks to compact the representation but I am not expecting many hook object, specially now that wildcard support for devices is in place. Note that the nft_trans_chain_hooks() list contains a list of struct nft_trans_hook objects for DELCHAIN and DELFLOWTABLE commands, while this list stores struct nft_hook objects for NEWCHAIN and NEWFLOWTABLE. Note that new commands can be updated to use nft_trans_hook for consistency. This patch also adapts the event notification path to deal with the list of hook transactions. Fixes: 7d937b107108 ("netfilter: nf_tables: support for deleting devices in an existing netdev chain") Fixes: b6d9014a3335 ("netfilter: nf_tables: delete flowtable hooks via transaction list") Reported-by: Xiang Mei Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: join hook list via splice_list_rcu() in commit phase

2026-04-21T10:48:44+00:00

Publish new hooks in the list into the basechain/flowtable using splice_list_rcu() to ensure netlink dump list traversal via rcu is safe while concurrent ruleset update is going on. Fixes: 78d9f48f7f44 ("netfilter: nf_tables: add devices to existing flowtable") Fixes: b9703ed44ffb ("netfilter: nf_tables: support for adding new devices to an existing netdev chain") Signed-off-by: Pablo Neira Ayuso

netfilter: nf_tables: use list_del_rcu for netlink hooks

2026-04-21T10:47:47+00:00

nft_netdev_unregister_hooks and __nft_unregister_flowtable_net_hooks need to use list_del_rcu(), this list can be walked by concurrent dumpers. Add a new helper and use it consistently. Fixes: f9a43007d3f7 ("netfilter: nf_tables: double hook unregistration in netns path") Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso

netfilter: nfnetlink_osf: fix potential NULL dereference in ttl check

2026-04-20T21:45:44+00:00

The nf_osf_ttl() function accessed skb->dev to perform a local interface address lookup without verifying that the device pointer was valid. Additionally, the implementation utilized an in_dev_for_each_ifa_rcu loop to match the packet source address against local interface addresses. It assumed that packets from the same subnet should not see a decrement on the initial TTL. A packet might appear it is from the same subnet but it actually isn't especially in modern environments with containers and virtual switching. Remove the device dereference and interface loop. Replace the logic with a switch statement that evaluates the TTL according to the ttl_check. Fixes: 11eeef41d5f6 ("netfilter: passive OS fingerprint xtables match") Reported-by: Kito Xu (veritas501) Closes: https://lore.kernel.org/netfilter-devel/20260414074556.2512750-1-hxzene@gmail.com/ Signed-off-by: Fernando Fernandez Mancera Reviewed-by: Pablo Neira Ayuso Signed-off-by: Pablo Neira Ayuso

netfilter: nfnetlink_osf: fix out-of-bounds read on option matching

2026-04-20T21:45:43+00:00

In nf_osf_match(), the nf_osf_hdr_ctx structure is initialized once and passed by reference to nf_osf_match_one() for each fingerprint checked. During TCP option parsing, nf_osf_match_one() advances the shared ctx->optp pointer. If a fingerprint perfectly matches, the function returns early without restoring ctx->optp to its initial state. If the user has configured NF_OSF_LOGLEVEL_ALL, the loop continues to the next fingerprint. However, because ctx->optp was not restored, the next call to nf_osf_match_one() starts parsing from the end of the options buffer. This causes subsequent matches to read garbage data and fail immediately, making it impossible to log more than one match or logging incorrect matches. Instead of using a shared ctx->optp pointer, pass the context as a constant pointer and use a local pointer (optp) for TCP option traversal. This makes nf_osf_match_one() strictly stateless from the caller's perspective, ensuring every fingerprint check starts at the correct option offset. Fixes: 1a6a0951fc00 ("netfilter: nfnetlink_osf: add missing fmatch check") Suggested-by: Florian Westphal Signed-off-by: Fernando Fernandez Mancera Reviewed-by: Pablo Neira Ayuso Signed-off-by: Pablo Neira Ayuso

ipvs: fix MTU check for GSO packets in tunnel mode

2026-04-20T21:45:43+00:00

Currently, IPVS skips MTU checks for GSO packets by excluding them with the !skb_is_gso(skb) condition. This creates problems when IPVS tunnel mode encapsulates GSO packets with IPIP headers. The issue manifests in two ways: 1. MTU violation after encapsulation: When a GSO packet passes through IPVS tunnel mode, the original MTU check is bypassed. After adding the IPIP tunnel header, the packet size may exceed the outgoing interface MTU, leading to unexpected fragmentation at the IP layer. 2. Fragmentation with problematic IP IDs: When net.ipv4.vs.pmtu_disc=1 and a GSO packet with multiple segments is fragmented after encapsulation, each segment gets a sequentially incremented IP ID (0, 1, 2, ...). This happens because: a) The GSO packet bypasses MTU check and gets encapsulated b) At __ip_finish_output, the oversized GSO packet is split into separate SKBs (one per segment), with IP IDs incrementing c) Each SKB is then fragmented again based on the actual MTU This sequential IP ID allocation differs from the expected behavior and can cause issues with fragment reassembly and packet tracking. Fix this by properly validating GSO packets using skb_gso_validate_network_len(). This function correctly validates whether the GSO segments will fit within the MTU after segmentation. If validation fails, send an ICMP Fragmentation Needed message to enable proper PMTU discovery. Fixes: 4cdd34084d53 ("netfilter: nf_conntrack_ipv6: improve fragmentation handling") Signed-off-by: Yingnan Zhang <342144303@qq.com> Acked-by: Julian Anastasov Signed-off-by: Pablo Neira Ayuso