linux/include/net/netfilter, branch master

netfilter: nft_set_pipapo: split gc into unlink and reclaim phase

2026-03-05T12:22:37Z

Yiming Qian reports Use-after-free in the pipapo set type: Under a large number of expired elements, commit-time GC can run for a very long time in a non-preemptible context, triggering soft lockup warnings and RCU stall reports (local denial of service). We must split GC in an unlink and a reclaim phase. We cannot queue elements for freeing until pointers have been swapped. Expired elements are still exposed to both the packet path and userspace dumpers via the live copy of the data structure. call_rcu() does not protect us: dump operations or element lookups starting after call_rcu has fired can still observe the free'd element, unless the commit phase has made enough progress to swap the clone and live pointers before any new reader has picked up the old version. This a similar approach as done recently for the rbtree backend in commit 35f83a75529a ("netfilter: nft_set_rbtree: don't gc elements on insert"). Fixes: 3c4287f62044 ("nf_tables: Add set type for arbitrary concatenation of ranges") Reported-by: Yiming Qian Signed-off-by: Florian Westphal

netfilter: nf_tables: clone set on flush only

2026-03-05T12:22:37Z

Syzbot with fault injection triggered a failing memory allocation with GFP_KERNEL which results in a WARN splat: iter.err WARNING: net/netfilter/nf_tables_api.c:845 at nft_map_deactivate+0x34e/0x3c0 net/netfilter/nf_tables_api.c:845, CPU#0: syz.0.17/5992 Modules linked in: CPU: 0 UID: 0 PID: 5992 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 RIP: 0010:nft_map_deactivate+0x34e/0x3c0 net/netfilter/nf_tables_api.c:845 Code: 8b 05 86 5a 4e 09 48 3b 84 24 a0 00 00 00 75 62 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc e8 63 6d fa f7 90 <0f> 0b 90 43 +80 7c 35 00 00 0f 85 23 fe ff ff e9 26 fe ff ff 89 d9 RSP: 0018:ffffc900045af780 EFLAGS: 00010293 RAX: ffffffff89ca45bd RBX: 00000000fffffff4 RCX: ffff888028111e40 RDX: 0000000000000000 RSI: 00000000fffffff4 RDI: 0000000000000000 RBP: ffffc900045af870 R08: 0000000000400dc0 R09: 00000000ffffffff R10: dffffc0000000000 R11: fffffbfff1d141db R12: ffffc900045af7e0 R13: 1ffff920008b5f24 R14: dffffc0000000000 R15: ffffc900045af920 FS: 000055557a6a5500(0000) GS:ffff888125496000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb5ea271fc0 CR3: 000000003269e000 CR4: 00000000003526f0 Call Trace: __nft_release_table+0xceb/0x11f0 net/netfilter/nf_tables_api.c:12115 nft_rcv_nl_event+0xc25/0xdb0 net/netfilter/nf_tables_api.c:12187 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 blocking_notifier_call_chain+0x6a/0x90 kernel/notifier.c:380 netlink_release+0x123b/0x1ad0 net/netlink/af_netlink.c:761 __sock_release net/socket.c:662 [inline] sock_close+0xc3/0x240 net/socket.c:1455 Restrict set clone to the flush set command in the preparation phase. Add NFT_ITER_UPDATE_CLONE and use it for this purpose, update the rbtree and pipapo backends to only clone the set when this iteration type is used. As for the existing NFT_ITER_UPDATE type, update the pipapo backend to use the existing set clone if available, otherwise use the existing set representation. After this update, there is no need to clone a set that is being deleted, this includes bound anonymous set. An alternative approach to NFT_ITER_UPDATE_CLONE is to add a .clone interface and call it from the flush set path. Reported-by: syzbot+4924a0edc148e8b4b342@syzkaller.appspotmail.com Fixes: 3f1d886cc7c3 ("netfilter: nft_set_pipapo: move cloning of match info to insert/removal path") Signed-off-by: Pablo Neira Ayuso Signed-off-by: Florian Westphal

Merge tag 'nf-next-26-02-06' of https://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-next

2026-02-11T04:25:38Z

Florian Westphal says: ==================== netfilter: updates for net-next The following patchset contains Netfilter updates for *net-next*: 1) Fix net-next-only use-after-free bug in nf_tables rbtree set: Expired elements cannot be released right away after unlink anymore because there is no guarantee that the binary-search blob is going to be updated. Spotted by syzkaller. 2) Fix esoteric bug in nf_queue with udp fraglist gro, broken since 6.11. Patch 3 adds extends the nfqueue selftest for this. 4) Use dedicated slab for flowtable entries, currently the -512 cache is used, which is wasteful. From Qingfang Deng. 5) Recent net-next update extended existing test for ip6ip6 tunnels, add the required /config entry. Test still passed by accident because the previous tests network setup gets re-used, so also update the test so it will fail in case the ip6ip6 tunnel interface cannot be added. 6) Fix 'nft get element mytable myset { 1.2.3.4 }' on big endian platforms, this was broken since code was added in v5.1. 7) Fix nf_tables counter reset support on 32bit platforms, where counter reset may cause huge values to appear due to wraparound. Broken since reset feature was added in v6.11. From Anders Grahn. 8-11) update nf_tables rbtree set type to detect partial operlaps. This will eventually speed up nftables userspace: at this time userspace does a netlink dump of the set content which slows down incremental updates on interval sets. From Pablo Neira Ayuso. * tag 'nf-next-26-02-06' of https://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-next: netfilter: nft_set_rbtree: validate open interval overlap netfilter: nft_set_rbtree: validate element belonging to interval netfilter: nft_set_rbtree: check for partial overlaps in anonymous sets netfilter: nft_set_rbtree: fix bogus EEXIST with NLM_F_CREATE with null interval netfilter: nft_counter: fix reset of counters on 32bit archs netfilter: nft_set_hash: fix get operation on big endian selftests: netfilter: add IPV6_TUNNEL to config netfilter: flowtable: dedicated slab for flow entry selftests: netfilter: nft_queue.sh: add udp fraglist gro test case netfilter: nfnetlink_queue: do shared-unconfirmed check before segmentation netfilter: nft_set_rbtree: don't gc elements on insert ==================== Link: https://patch.msgid.link/20260206153048.17570-1-fw@strlen.de Signed-off-by: Jakub Kicinski

net/ipv6: Introduce payload_len helpers

2026-02-07T04:50:03Z

The next commits will transition away from using the hop-by-hop extension header to encode packet length for BIG TCP. Add wrappers around ip6->payload_len that return the actual value if it's non-zero, and calculate it from skb->len if payload_len is set to zero (and a symmetrical setter). The new helpers are used wherever the surrounding code supports the hop-by-hop jumbo header for BIG TCP IPv6, or the corresponding IPv4 code uses skb_ip_totlen (e.g., in include/net/netfilter/nf_tables_ipv6.h). No behavioral change in this commit. Signed-off-by: Alice Mikityanska Acked-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260205133925.526371-2-alice.kernel@fastmail.im Signed-off-by: Jakub Kicinski

netfilter: nft_set_rbtree: validate open interval overlap

2026-02-06T12:36:07Z

Open intervals do not have an end element, in particular an open interval at the end of the set is hard to validate because of it is lacking the end element, and interval validation relies on such end element to perform the checks. This patch adds a new flag field to struct nft_set_elem, this is not an issue because this is a temporary object that is allocated in the stack from the insert/deactivate path. This flag field is used to specify that this is the last element in this add/delete command. The last flag is used, in combination with the start element cookie, to check if there is a partial overlap, eg. Already exists: 255.255.255.0-255.255.255.254 Add interval: 255.255.255.0-255.255.255.255 ~~~~~~~~~~~~~ start element overlap Basically, the idea is to check for an existing end element in the set if there is an overlap with an existing start element. However, the last open interval can come in any position in the add command, the corner case can get a bit more complicated: Already exists: 255.255.255.0-255.255.255.254 Add intervals: 255.255.255.0-255.255.255.255,255.255.255.0-255.255.255.254 ~~~~~~~~~~~~~ start element overlap To catch this overlap, annotate that the new start element is a possible overlap, then report the overlap if the next element is another start element that confirms that previous element in an open interval at the end of the set. For deletions, do not update the start cookie when deleting an open interval, otherwise this can trigger spurious EEXIST when adding new elements. Unfortunately, there is no NFT_SET_ELEM_INTERVAL_OPEN flag which would make easier to detect open interval overlaps. Fixes: 7c84d41416d8 ("netfilter: nft_set_rbtree: Detect partial overlaps on insertion") Signed-off-by: Pablo Neira Ayuso Signed-off-by: Florian Westphal

netfilter: nfnetlink_queue: do shared-unconfirmed check before segmentation

2026-02-06T12:34:55Z

Ulrich reports a regression with nfqueue: If an application did not set the 'F_GSO' capability flag and a gso packet with an unconfirmed nf_conn entry is received all packets are now dropped instead of queued, because the check happens after skb_gso_segment(). In that case, we did have exclusive ownership of the skb and its associated conntrack entry. The elevated use count is due to skb_clone happening via skb_gso_segment(). Move the check so that its peformed vs. the aggregated packet. Then, annotate the individual segments except the first one so we can do a 2nd check at reinject time. For the normal case, where userspace does in-order reinjects, this avoids packet drops: first reinjected segment continues traversal and confirms entry, remaining segments observe the confirmed entry. While at it, simplify nf_ct_drop_unconfirmed(): We only care about unconfirmed entries with a refcnt > 1, there is no need to special-case dying entries. This only happens with UDP. With TCP, the only unconfirmed packet will be the TCP SYN, those aren't aggregated by GRO. Next patch adds a udpgro test case to cover this scenario. Reported-by: Ulrich Weber Fixes: 7d8dc1c7be8d ("netfilter: nf_queue: drop packets with cloned unconfirmed conntracks") Signed-off-by: Florian Westphal

netfilter: nfnetlink_queue: optimize verdict lookup with hash table

2026-01-29T08:52:07Z

The current implementation uses a linear list to find queued packets by ID when processing verdicts from userspace. With large queue depths and out-of-order verdicting, this O(n) lookup becomes a significant bottleneck, causing userspace verdict processing to dominate CPU time. Replace the linear search with a hash table for O(1) average-case packet lookup by ID. A global rhashtable spanning all network namespaces attributes hash bucket memory to kernel but is subject to fixed upper bound. Signed-off-by: Scott Mitchell Signed-off-by: Florian Westphal

netfilter: nf_tables: add .abort_skip_removal flag for set types

2026-01-22T16:18:13Z

The pipapo set backend is the only user of the .abort interface so far. To speed up pipapo abort path, removals are skipped. The follow up patch updates the rbtree to use to build an array of ordered elements, then use binary search. This needs a new .abort interface but, unlike pipapo, it also need to undo/remove elements. Add a flag and use it from the pipapo set backend. Signed-off-by: Pablo Neira Ayuso Signed-off-by: Florian Westphal

netfilter: nf_conntrack: don't rely on implicit includes

2026-01-20T15:23:37Z

several netfilter compilation units rely on implicit includes coming from nf_conntrack_proto_gre.h. Clean this up and add the required dependencies where needed. nf_conntrack.h requires net_generic() helper. Place various gre/ppp/vlan includes to where they are needed. Signed-off-by: Florian Westphal

netfilter: don't include xt and nftables.h in unrelated subsystems

2026-01-20T15:23:37Z

conntrack, xtables and nftables are distinct subsystems, don't use them in other subystems. Signed-off-by: Florian Westphal