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8 daysnetfilter: nf_tables: skip double clone set expressions on element insertPablo Neira Ayuso1-2/+0
Both the dynset and newsetelem path clone the existing set expressions when setting set element expressions if no override expressions are provided. This results in a double clone, once to clone the template set expressions then another clone on the new element. Add a flag to annotate if userspace provides a override expression (ie. expression of the same type of the set but different configuration), otherwise borrow the existing expression from the set. Add conditionals to release expression iif they represent an override. Use this new override_exprs flag to dump the dynset expression override to userspace. This simplifies the existing logic and it also fixes a bug with the connlimit expression which results in a module refcount imbalance WARNING splat when resorting on the default set expressions. Fixes: 65038428b2c6 ("netfilter: nf_tables: allow to specify stateful expression in set definition") Fixes: fca05d4d61e6 ("netfilter: nft_dynset: honor stateful expressions in set definition") Reported-by: Xingyuan Mo <hdthky0@gmail.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-08-18netfilter: nf_tables: move set_update_list to nftables per-netnsPablo Neira Ayuso1-0/+1
This list is used to invoke the set .commit and .abort ops for the rbtree and pipapo to run GC on expired elements and replace the current datastructure view by the clone. For the rbtree, this also rebuild the datapath b-search array. From abort path, remove the set from the update_list if it is already bound to rule, then the rule itself takes care of releasing the set and its elements, otherwise, memleak is possible because set ops .abort only deals with removing the set data structure, not the elements. This is a preparation patch to call set .commit before processing the transaction list for the rbtree, no functional changes are intended. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-08-10netfilter: nft_ct: move custom expectation support to helperPablo Neira Ayuso1-0/+1
Originally, the ct expectation support called nf_ct_helper_ext_add() for confirmed conntracks, which is invalid, triggering a splat. This was fixed by commit 1710eb913bdc ("netfilter: nft_ct: skip expectations for confirmed conntrack") which restricted it to unconfirmed conntracks. However, early insertion of expectations into the expectations list when the conntrack is unconfirmed leads to stale entries pointing to the wrong hlist_head through .pprev due to ct extension reallocation. Commit 7c9664351980 ("netfilter: move nat hlist_head to nf_conn") moved the nat hlist_head to nf_conn for this reason: 1. ... 2. When reallocation of extension area occurs we need to fixup the bysource hash head via hlist_replace_rcu. I'd rather not increase the size of the struct nf_conn for this feature has very limited scope: only one expectation can be created at a time given expect_clash() will make nf_ct_expect_related() reports EBUSY. For this reason, relax nf_ct_expect_related() not to drop packets in case expectation creation fails, therefore, expectation creation becomes best effort. To address this issue, add an internal ct helper and attach it to the conntrack entry to streamline the custom ct expectation support with existing ct helpers. Expose a new nf_conntrack_helper_release() function to release the internal helper that is allocated and attached to the conntrack entry to create the custom expectations. The nft_ct module removal always waits for rcu grace period, then the NULL helper callback is observed after this. This patch also restricts the creation of expectations to different helpers other than this custom helper that is created for this type of expectations. Fixes: 857b46027d6f ("netfilter: nft_ct: add ct expectations support") Reported-by: Jaeyeong Lee <iostreampy@proton.me> Link: https://patch.msgid.link/20260715144755.00ea7dfcd9f@proton.me Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-08-10netfilter: flowtable: rename tun.l3_proto to tun.inner_protoPablo Neira Ayuso1-1/+1
This field refers to the inner protocol that is encapsulated by the tunnel header, just a comestic change. No functional changes are expected. Acked-by: Lorenzo Bianconi <lorenzo@kernel.org> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-07-30Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski2-1/+6
Cross-merge networking fixes after downstream PR (net-7.2-rc6). No conflicts. Adjacent changes: net/ipv4/route.c dbc3791e3b24 ("net: do not send ICMP/NDISC Redirects when peer allocation fails") 7804eaa057fe ("ipv4: snapshot dst.dev in ip_rt_send_redirect() and ip_rt_get_source()") drivers/net/tun.c 23dad2d088df ("tun: no longer rely on RTNL in tun_fill_info()") c3da92af07ea ("Revert "tun/tap: add ptr_ring consume helper with netdev queue wakeup"") drivers/net/ethernet/marvell/octeontx2/af/rvu_npc.c 3bd438a58e91 ("octeontx2-af: Block VFs from clobbering special CGX PKIND state") 5ba5611ef946 ("octeontx2-af: reserve 4 PKINDs for skip-size custom use") drivers/net/wireless/ath/ath12k/core.h drivers/net/wireless/ath/ath12k/mac.c drivers/net/wireless/ath/ath12k/peer.c 469d7e6077c1 ("wifi: ath12k: resolve PENDING ML peer ID from MLO_PEER_MAP HTT event") 378e659029d5 ("wifi: ath12k: introduce host_alloc_ml_id hardware parameter") c42b27336eef ("wifi: ath12k: fix survey indexing across bands") Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-07-24netfilter: nf_conntrack_expect: store event cache in expectationPablo Neira Ayuso1-0/+3
Store the event cache in the expectation instead of accessing the exp->master cache, as a step forward towards turning the exp->master into a cookie. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-07-24netfilter: flowtable: tear down flow entries with stale dst from GCPablo Neira Ayuso1-0/+8
In case of route updates, tear down flow entries with stale dst to give them a chance to obtain a fresh route. This is specifically useful for hardware offloaded entries, where the flowtable software dataplane sees no packet, where the existing check for stale dst entries does not help. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-07-23netfilter: nf_tables: make nft_object rhltable per tablePablo Neira Ayuso1-1/+3
The nft_object rhltable is global, this allows for accessing objects that are being dismangled from lookup path by other existing netns. Given the nft_obj_destroy() releases the object inmediately, this might lead to use-after-free of these objects that are being released. Make the existing rhltable per table to address this issue to deal with with the nft_rcv_nl_event() path too. Update nft_obj_lookup() to take the table as non-const, otherwise, compiler complains when passing the objname_ht to rhltable_lookup(). Fixes: 4d44175aa5bb ("netfilter: nf_tables: handle nft_object lookups via rhltable") Suggested-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-07-22netfilter: nf_conntrack_expect: add and use nf_ct_expect_related_pair()Pablo Neira Ayuso1-0/+3
Add a new function to insert a pair of expectations, this is required by the SIP and H323 NAT helpers. The spinlock is held to check if there is a slot for both expectations, in such case, insert them. This removes the need for nf_ct_unexpect_related() inside the loop to find a pair of consecutive ports, otherwise inserting expectations whose dead flag is already set on can happen. Bump master_help->expecting for the expectation class after checking if the expectation fits in the master expectation list, which is needed for this new _pair() function variant to run the eviction routine including the preallocated slot for the first expectation in the pair. Fixes: b8b09dc2bf35 ("netfilter: nf_conntrack_expect: use conntrack GC to reap expectations") Reported-by: Jaeyeong Lee <iostreampy@proton.me> Link: https://patch.msgid.link/178377968720.33756.12204817361601593230@proton.me/ Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-07-10Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netPaolo Abeni1-2/+5
Cross-merge networking fixes after downstream PR (net-7.2-rc3). Conflicts: tools/testing/selftests/net/lib.sh dd6a23bac306b ("selftests: net: make busywait timeout clock portable") 895bad9cc4cec ("selftests: net: make busywait timeout clock portable") Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2026-07-08netfilter: flowtable: support IPIP tunnel with direct xmitPablo Neira Ayuso1-2/+3
The combination of IPIP tunnel with direct xmit, eg. bridge device, breaks because no dst_entry is provided to check the skb headroom and to set the iph->frag_off field. This leads to invalid dst usage and can trigger a crash in the tunnel transmit path. Fix this by moving dst_cache and dst_cookie out of the runtime union so that they can be shared by neighbour, xfrm, and direct tunnel flows. For FLOW_OFFLOAD_XMIT_DIRECT tuples carrying tunnel metadata, preserve route state in these shared fields and release it through the common dst release path. Since dst_entry is now available to the three supported xmit modes and dst_release() already deals with NULL dst, remove the xmit type check in nft_flow_dst_release(). Moreover, skip the check if the dst entry is NULL in nf_flow_dst_check() which is now the case for the direct xmit case. Based on patch from Rein Wei <n05ec@lzu.edu.cn>. Fixes: d30301ba4b07 ("netfilter: flowtable: Add IPIP tx sw acceleration") Cc: stable@vger.kernel.org Reported-by: Yuan Tan <yuantan098@gmail.com> Reported-by: Xin Liu <bird@lzu.edu.cn> Reported-by: Zhengyang Chen <chzhengyang2023@lzu.edu.cn> Reported-by: Ren Wei <n05ec@lzu.edu.cn> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Acked-by: Lorenzo Bianconi <lorenzo@kernel.org> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-07-08netfilter: flowtable: IPIP tunnel hardware offload is not yet supportPablo Neira Ayuso1-0/+2
No driver supports for IPIP tunnels yet, give up early on setting up the hardware offload for this scenario. This patch adds a stub that can be enhanced to add more configuration that are currently not supported. As of now, the offload work is enqueued to the worker, then ignored if the hardware offload configuration is not supported. Check the NF_FLOW_HW flag to know if this entry was already tried once to be offloaded so this is not retried on refresh when unsupported. Move NF_FLOW_HW flag check to nf_flow_offload_add(). If this NF_FLOW_HW flag is unset the _del and _stats variants are never called. This can be updated later on to skip hardware offload work to be queued in case hardware offload does not support it. Fixes: d98103575dcd ("netfilter: flowtable: Add IP6IP6 rx sw acceleration") Fixes: ab427db17885 ("netfilter: flowtable: Add IPIP rx sw acceleration") Cc: stable@vger.kernel.org Reported-by: Yuan Tan <yuantan098@gmail.com> Reported-by: Xin Liu <bird@lzu.edu.cn> Reported-by: Zhengyang Chen <chzhengyang2023@lzu.edu.cn> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Acked-by: Lorenzo Bianconi <lorenzo@kernel.org> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-07-02netfilter: conntrack: remove obsolete module parametersFlorian Westphal1-1/+0
helper autoassign was removed years ago, all the port numbers are no longer functional. Signed-off-by: Florian Westphal <fw@strlen.de>
2026-07-02netfilter: conntrack: get rid of tuple in helper definitionsFlorian Westphal1-5/+4
Leftover from the days when the kernel did automatic assignment of helpers based on a pre-registered / well-known-port. This helper autoassign was removed from the kernel, so all we really need are the l3 and l4 protocol numbers. In the broadcast helper, the only remaining consumer of the port number is removed. AFAICS its not needed: The expectation is populated from the control connection reply tuple, so the src port is the original directions destination (snmp/161 for example). LLM complained about silent l3num (u16) -> nfproto (u8) truncation, so add a netlink policy validation to reject large NFPROTO values upfront. Assisted-by: Claude:claude-sonnet-4-6 Signed-off-by: Florian Westphal <fw@strlen.de>
2026-06-23netfilter: nf_conntrack_expect: store master_tuple in expectationPablo Neira Ayuso1-0/+1
Store master conntrack tuple in the expectation since exp->master might refer to a different conntrack when accessed from rcu read side lock area due to typesafe rcu rules. Fixes: 02a3231b6d82 ("netfilter: nf_conntrack_expect: store netns and zone in expectation") Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-23netfilter: conntrack: add deprecation warnings for irc and pptp trackersFlorian Westphal1-0/+4
IRC Direct client-to-client requires plaintext. IRC over TLS should be preferred, making this helper ineffective. Add a deprecation warning and update the help text to better reflect that this is needed for the DCC extension, not IRC itself. PPTP is esoteric these days and it is the only helper that requires the destroy callback in the conntrack helper API. Removal would simplify the conntrack core. Both helpers are IPv4 only. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-21netfilter: nf_conntrack_expect: use conntrack GC to reap expectationsPablo Neira Ayuso1-3/+13
This patch replaces the timer API by GC worker approach for expectations, as it already happened in many other subsystems. Use the existing conntrack GC worker to iterate over the local list of expectations in the master conntrack to reap expired expectations. Check IPS_HELPER_BIT to run GC for expectations, set it on for nft_ct expectation which nevers sets it. Hold the expectation spinlock while iterating over the master conntrack expectation list to synchronize with nf_ct_remove_expectations(). This also performs runtime packet path garbage collection through the expectation insertion and lookup functions while walking over one of the chains of the global expectation hashtables. Unconfirmed conntrack entries are skipped since ct->ext can be reallocated and dying are skipped since those will be gone soon. Set on IPS_HELPER_BIT if the helper ct extension is added, then the new GC worker does not need to bump the ct refcount to check if the ct->ext helper is available. This removes the extra bump on the refcount for expectation timers, this allows to remove several nf_ct_expect_put() calls after the unlink, after this update only refcount remains at 1 while on the expectation hashes. This patch implicitly addresses a race with the existing timer API allowing an expectation to access a stale exp->master pointer which has been already released when expectation removal loses races with an expiring timer, ie. timer_del() reporting false. Add a new NF_CT_EXPECT_DEAD flag to reap this expectation via GC. This is needed by nf_conntrack_unexpect_related() which is called in error paths to invalidate newly created expectations that has been added into the hashes. These expectactions cannot be inmediately released as GC or nf_ct_remove_expectations() could race to make it. On expectation insert, the runtime GC reaps stale expectations before checking the expectation limit set by policy. Set current timestamp in nf_ct_expect_alloc(), then add the expectation policy timeout (or custom timeout specified added on top of this) to specify the expectation lifetime. Fixes: bffcaad9afdf ("netfilter: ctnetlink: ensure safe access to master conntrack") Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-21netfilter: nft_meta_bridge: add validate callback for get operationsFlorian Westphal1-0/+2
Blamed commit added NFT_META_BRI_IIFHWADDR to the set validate callback, yet this is a get operation. Add a get validate callback and move the NFT_META_BRI_IIFHWADDR key there. AFAICS this is harmless, NFT_META_BRI_IIFHWADDR can deal with a NULL input device and the set handler ignores a NFT_META_BRI_IIFHWADDR operation, but it allows to read 4 bytes off bridge skb->cb[]. Fixes: cbd2257dc96e ("netfilter: nft_meta_bridge: introduce NFT_META_BRI_IIFHWADDR support") Signed-off-by: Florian Westphal <fw@strlen.de> Reviewed-by: Fernando Fernandez Mancera <fmancera@suse.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-19netfilter: nf_queue: pin bridge device while NFQUEUE holds fake dstHaoze Xie1-0/+1
The br_netfilter fake rtable is embedded in struct net_bridge and is attached to bridged packets with skb_dst_set_noref(). If such a packet is queued to NFQUEUE, __nf_queue() upgrades that fake dst with skb_dst_force(). At that point the queued skb can hold a real dst reference after bridge teardown has started. The problem is not that every bridged packet needs its own dst reference. The problem is that NFQUEUE can keep the bridge private fake dst alive after unregister begins. Fix this by keeping the bridge fake dst model unchanged and pinning the bridge master device only while the packet sits in NFQUEUE. Record the bridge device in nf_queue_entry when the queued skb carries a bridge fake dst, take a device reference for the queue lifetime, and drop it when the queue entry is freed. Also make sure queued entries are reaped when that bridge device goes down, and drop the redundant nf_bridge_info_exists() test from the fake dst detection. This keeps netdev_priv(br->dev) alive until verdict completion, so the embedded fake rtable and its metrics backing storage cannot be freed out from under dst_release(). It also avoids the constant refcount bump and avoids using ipv4-specific dst helpers for IPv6 bridge traffic. Fixes: 34666d467cbf ("netfilter: bridge: move br_netfilter out of the core") Cc: stable@kernel.org Reported-by: Yuan Tan <yuantan098@gmail.com> Reported-by: Yifan Wu <yifanwucs@gmail.com> Reported-by: Juefei Pu <tomapufckgml@gmail.com> Reported-by: Xin Liu <bird@lzu.edu.cn> Signed-off-by: Haoze Xie <royenheart@gmail.com> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-15Merge tag 'nf-next-26-06-14' of git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-nextJakub Kicinski2-5/+31
Pablo Neira Ayuso says: ==================== Netfilter/IPVS updates for net-next The following patchset contains Netfilter/IPVS updates for net-next. More specifically, this contains conncount rework to address AI related reports, assorted Netfiter updates and two small incremental updates on IPVS: 1) Replace old obsolete workqueues (system_wq, system_unbound_wq) in IPVS, from Marco Crivellari. 2) Replace WARN_ON{_ONCE} by DEBUG_NET_WARN_ON_ONCE in nf_tables. In the recent years, reporters say that the use of WARN_ON{_ONCE} in conjunction with panic_on_warn=1 results in DoS. Let's replace it by DEBUG_NET_WARN_ON_ONCE so this is only exercised by test infrastructure and fuzzers, while also providing context to AI agents. From Fernando F. Mancera. Five patches from Florian Westphal to address AI reports in the conncount infrastructures: 3) Fix missing rcu read lock section when calling __ovs_ct_limit_get_zone_limit(). 4) Add a dedicate lock per rbtree tree, this increases memory usage but it should improve scalability. 5) Add a helper function to find the rbtree node, no functional changes are intented. 6) Add sequence counter to detect concurrent tree modifications and retry lookups. 7) Add locks to GC conncount walk and address other nitpicks. Then, several assorted updates: 8) Defensive Tree-wide addition of NULL checks for ct extensions. 9) Bail out if flowtable bypass cannot be fully set up from the flow offload expression, instead of lazy building a likely incomplete one. 10) Fix documentation for the new conn_max sysctl toggle in IPVS. 11) Add nf_dev_xmit_recursion*() helpers and use them, to address recent AI reports. * tag 'nf-next-26-06-14' of git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-next: netfilter: nf_dup_netdev: add nf_dev_xmit_recursion*() helpers and use them ipvs: fix doc syntax for conn_max sysctl netfilter: flowtable: bail out if forward path cannot be discovered netfilter: conntrack: check NULL when retrieving ct extension netfilter: nf_conncount: gc and rcu fixes netfilter: nf_conncount: add sequence counter to detect tree modifications netfilter: nf_conncount: split count_tree_node rbtree walk into helper netfilter: nf_conncount: use per nf_conncount_data spinlocks netfilter: nf_conncount: callers must hold rcu read lock netfilter: nf_tables: use DEBUG_NET_WARN_ON_ONCE in packet and control paths ipvs: Replace use of system_unbound_wq with system_dfl_long_wq ==================== Link: https://patch.msgid.link/20260614114605.474783-1-pablo@netfilter.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-06-14netfilter: nf_dup_netdev: add nf_dev_xmit_recursion*() helpers and use themPablo Neira Ayuso1-5/+29
Update nft_dup and nft_fwd to use the nf_dev_xmit_recursion() helpers. This patch also disables BH when transmitting the skb to address a possible migration to different CPU leading to imbalanced decrementation of the recursion counters. This is modeled after Florian Westphal's dev_xmit_recursion*() API available since commit 97cdcf37b57e ("net: place xmit recursion in softnet data") according to its current state in the tree. Fixes: 1d47b55b36d2 ("netfilter: nft_fwd_netdev: use recursion counter in neigh egress path") Fixes: f37ad9127039 ("netfilter: nf_dup_netdev: Move the recursion counter struct netdev_xmit") Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-14netfilter: conntrack: check NULL when retrieving ct extensionPablo Neira Ayuso1-0/+2
nf_ct_ext_find() might return NULL if ct extension is not found. Add also the null checks to: - nfct_help() - nfct_help_data() - nfct_seqadj() - nfct_nat() This is defensive, for safety reasons. nf_ct_ext_find() used to return NULL if the extension is stale for unconfirmed conntracks if the genid validation fails. Skip NULL check in nf_nat_inet_fn() given this is valid to be NULL for non-initialized ct nat extensions. While at it, fetch ct helper area in nf_ct_expect_related_report() only once and pass it on to other ancilliary functions. Replace WARN_ON() by WARN_ON_ONCE() in nf_ct_unlink_expect_report(). Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-11Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski1-0/+1
Cross-merge networking fixes after downstream PR (net-7.1-rc8). Conflicts: drivers/net/ethernet/wangxun/txgbe/txgbe_aml.c f67aead16e85 ("net: txgbe: rework service event handling") 57d39faed4c9 ("net: txgbe: improve functions of AML 40G devices") net/rds/info.c 512db8267b73 ("rds: mark snapshot pages dirty in rds_info_getsockopt()") 6e94eeb2a2a6 ("rds: convert to getsockopt_iter") Adjacent changes: include/net/sock.h 1ee90b77b727 ("net: guard timestamp cmsgs to real error queue skbs") f0de88303d5e ("net: make is_skb_wmem() available to modules") Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-06-10netfilter: nf_conntrack: destroy stale expectfn expectations on unregisterWeiming Shi1-0/+1
NAT helpers such as nf_nat_h323 store a raw pointer to module text in exp->expectfn (e.g. ip_nat_q931_expect). nf_ct_helper_expectfn_unregister() only unlinks the callback descriptor and never walks the expectation table, so an expectation pending at module removal survives with a dangling exp->expectfn into freed module text. When the expected connection arrives, init_conntrack() invokes exp->expectfn(), now a stale pointer into the unloaded module. Reproduced on a KASAN build by loading the H.323 helpers, creating a Q.931 expectation, unloading nf_nat_h323, then connecting to the expected port: Oops: int3: 0000 [#1] SMP KASAN NOPTI RIP: 0010:0xffffffffa06102d1 init_conntrack.isra.0 (net/netfilter/nf_conntrack_core.c:1862) nf_conntrack_in (net/netfilter/nf_conntrack_core.c:2049) ipv4_conntrack_local (net/netfilter/nf_conntrack_proto.c:223) nf_hook_slow (net/netfilter/core.c:619) __ip_local_out (net/ipv4/ip_output.c:120) __tcp_transmit_skb (net/ipv4/tcp_output.c:1715) tcp_connect (net/ipv4/tcp_output.c:4374) tcp_v4_connect (net/ipv4/tcp_ipv4.c:345) __sys_connect (net/socket.c:2167) Modules linked in: nf_conntrack_h323 [last unloaded: nf_nat_h323] Reaching the dangling state requires CAP_SYS_MODULE in the initial user namespace to remove a NAT helper that still has live expectations, so this is a robustness fix; leaving an expectation pointing at freed text is wrong regardless. Add nf_ct_helper_expectfn_destroy(), which walks the expectation table and drops every expectation whose ->expectfn matches the descriptor being torn down. Call it from each NAT helper's exit path after the existing RCU grace period, so no expectation outlives the code it points at and no extra synchronize_rcu() is introduced. With the fix, the same reproducer runs to completion without the Oops. Fixes: f587de0e2feb ("[NETFILTER]: nf_conntrack/nf_nat: add H.323 helper port") Reported-by: Xiang Mei <xmei5@asu.edu> Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Weiming Shi <bestswngs@gmail.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-05netfilter: conntrack: revert ct extension genid infrastructurePablo Neira Ayuso1-12/+0
This infrastructure is not used anymore after moving ct timeout and helper to use datapath refcount to track object use. Revert commit c56716c69ce1 ("netfilter: extensions: introduce extension genid count") this patch disables all ct extensions (leading to NULL) for unconfirmed conntracks, when this is only targeted at ct helper and ct timeout. There is also codebase that dereferences the ct extension without checking for NULL which could lead to crash. Fixes: c56716c69ce1 ("netfilter: extensions: introduce extension genid count") Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-05netfilter: nf_conntrack_helper: add refcounting from datapathPablo Neira Ayuso1-5/+21
This patch adds a new ->ct_refcnt field to struct nf_conntrack_helper which is bumped when the helper is used by the ct helper extension. Drop this reference count when the conntrack entry is released. This is a packet path refcount which ensures that struct nf_conntrack_helper remains in place for tricky scenarios where a packet sits in nfqueue, or elsewhere, with a conntrack that refers to this helper. For simplicity, this leaves a single refcount for helper objects in place, remove the existing refcount for control plane that ensures that the helper does not go away if it is used by ruleset. On helper removal, the help callback is set to NULL to disable it from packet path and, after rcu grace period, existing expectations are removed. Update ctnetlink to disable access to .to_nlattr and .from_nlattr if the helper is going away. Remove nf_queue_nf_hook_drop() since it has proven not to be effective because packets with unconfirmed conntracks which are still flying to sit in nfqueue. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-05netfilter: nf_conntrack_pptp: move GRE specific cleanup to GRE trackerPablo Neira Ayuso1-0/+4
Move the GRE specific cleanup to nf_conntrack_proto_gre.c to ensure that the .destroy callback for the pptp helper is still reachable by existing conntrack entries while pptp module is being removed. This is a preparation patch, no functional changes are intended. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-05netfilter: nf_conntrack_helper: dynamically allocate struct nf_conntrack_helperPablo Neira Ayuso1-7/+9
Adapt all existing helpers to use a modified version of nf_ct_helper_init(), to dynamically allocate struct nf_conntrack_helper. Allocate expect_policy[] built-in into the helper to ensure this area is reachable after helper removal since a follow up patch adds refcount to track use of the nf_conntrack_helper structure from packet path so it remains around until last reference from ct helper extension is dropped. Export __nf_conntrack_helper_register() which allows to register nfnetlink_cthelper dynamically allocated helper. Adapt nfnetlink_cthelper to use the built-in expect_policy[]. This is a preparation patch to add packet path refcounting to helpers. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-06-05netfilter: cttimeout: detach dataplane timeout policy and repurpose refcountPablo Neira Ayuso1-2/+25
Add a refcount for struct nf_ct_timeout which is used by ct extension to set the custom ct timeout policy, this tells us that the ct timeout is being used by a conntrack entry. When the last conntrack entry drops the refcount on the ct timeout, the ct timeout is released. Remove the refcount for control plane which controls if the ruleset refers to the timeout policy. After this update, it is possible to remove the ct timeout policy from nfnetlink_cttimeout immediately. This is for simplicity not to handle two refcounts on a single object. Remove nf_queue_nf_hook_drop(): a packet sitting in nfqueue will just hold a reference to the nf_ct_timeout object until packet is reinjected, since this is part of the ct extension, this will be released by the time the conntrack is freed. nf_ct_untimeout() is still called to clean up in a best effort basis: the ct timeout on existing entries gets removed when the ct timeout goes away, but as long as the iptables ruleset still refers to the ct timeout through a template, new conntracks may keep attaching it and extend its lifetime until the rule is removed. nf_ct_untimeout() is not called anymore from module removal path, this is unlikely to find timeouts give module refcount is bumped, and the new refcount already tracks the ct timeout policy use so it is released when unused. Fixes: 50978462300f ("netfilter: add cttimeout infrastructure for fine timeout tuning") Fixes: 7e0b2b57f01d ("netfilter: nft_ct: add ct timeout support") Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-05-22netfilter: nf_tables: fix dst corruption in same register operationFernando Fernandez Mancera1-0/+7
For lshift and rshift, the shift operations are performed in a loop over 32-bit words. The loop calculates the shifted value and write it to dst, and then immediately reads from src to calculate the carry for the next iteration. Because src and dst could point to the same memory location, the carry is incorrectly calculated using the newly modified dst value instead of the original src value. Adding a temporary local variable to cache the original value before writing to dst and using it for the carry calculation solves the problem. In addition, partial overlap is rejected from control plane for all kind of operations including byteorder. This was tested with the following bytecode: table test_table ip flags 0 use 1 handle 1 ip test_table test_chain use 3 type filter hook input prio 0 policy accept packets 0 bytes 0 flags 1 ip test_table test_chain 2 [ immediate reg 1 0x44332211 0x88776655 ] [ bitwise reg 1 = ( reg 1 << 0x08000000 ) ] [ cmp eq reg 1 0x66443322 0x00887766 ] [ counter pkts 0 bytes 0 ] ip test_table test_chain 4 3 [ immediate reg 1 0x44332211 0x88776655 ] [ bitwise reg 1 = ( reg 1 << 0x08000000 ) ] [ cmp eq reg 1 0x55443322 0x00887766 ] [ counter pkts 21794 bytes 1917798 ] Fixes: 567d746b55bc ("netfilter: bitwise: add support for shifts.") Acked-by: Jeremy Sowden <jeremy@azazel.net> Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-05-16netfilter: nf_queue: hold bridge skb->dev while queuedHaoze Xie1-0/+1
br_pass_frame_up() rewrites skb->dev from the ingress port to the bridge master before queueing bridge LOCAL_IN packets. NFQUEUE only holds references on state.in/out and bridge physdevs, so a queued bridge packet can retain a freed bridge master in skb->dev until reinjection. When the verdict is reinjected later, br_netif_receive_skb() re-enters the receive path with skb->dev still pointing at the freed bridge master, triggering a use-after-free. Store skb->dev in the queue entry, hold a reference on it for the queue lifetime, and use the saved device when dropping queued packets during NETDEV_DOWN handling. Fixes: ac2863445686 ("netfilter: bridge: add nf_afinfo to enable queuing to userspace") Cc: stable@kernel.org Reported-by: Yuan Tan <yuantan098@gmail.com> Reported-by: Yifan Wu <yifanwucs@gmail.com> Reported-by: Juefei Pu <tomapufckgml@gmail.com> Reported-by: Xin Liu <bird@lzu.edu.cn> Signed-off-by: Haoze Xie <royenheart@gmail.com> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-05-08netfilter: nf_conntrack_expect: restore helper propagation via expectationPablo Neira Ayuso1-1/+4
A recent series to fix expectations broke helper propagation via expectation, this mechanism is used by the sip and h323 helper. This also propagates the conntrack helper to expected connections. I changed semantics of exp->helper which now tells us the actual helper that created the expectation. Add an explicit assign_helper field to expectations for this purpose and update helpers to use it. Restore this feature for userspace conntrack helper via ctnetlink nfqueue integration so it is again possible to attach a helper to an expectation, where it makes sense. This is not restored via ctnetlink expectation creation as there is no client for such feature. Use the expectation layer 4 protocol number for the helper lookup for consistency. Make sure the expectation using this helper propagation mechanism also go away when the helper is unregistered. Fixes: 9c42bc9db90a ("netfilter: nf_conntrack_expect: honor expectation helper field") Fixes: 917b61fa2042 ("netfilter: ctnetlink: ignore explicit helper on new expectations") Reported-by: Ilya Maximets <i.maximets@ovn.org> Tested-by: Ilya Maximets <i.maximets@ovn.org> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-05-01netfilter: flowtable: fix inline pppoe encapsulation in xmit pathPablo Neira Ayuso1-1/+3
Address two issues in the inline pppoe encapsulation: - Add needs_gso_segment flag to segment PPPoE packets in software given that there is no GSO support for this. - Use FLOW_OFFLOAD_XMIT_DIRECT since neighbour cache is not available in point-to-point device, use the hardware address that is obtained via flowtable path discovery (ie. fill_forward_path). Fixes: 18d27bed0880 ("netfilter: flowtable: inline pppoe encapsulation in xmit path") Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-04-30netfilter: nft_fwd_netdev: use recursion counter in neigh egress pathWeiming Shi1-0/+13
nft_fwd_neigh can be used in egress chains (NF_NETDEV_EGRESS). When the forwarding rule targets the same device or two devices forward to each other, neigh_xmit() triggers dev_queue_xmit() which re-enters nf_hook_egress(), causing infinite recursion and stack overflow. Move the nf_get_nf_dup_skb_recursion() accessor and NF_RECURSION_LIMIT to the shared header nf_dup_netdev.h as a static inline, so that nft_fwd_netdev can use the recursion counter directly without exported function call overhead. Guard neigh_xmit() with the same recursion limit already used in nf_do_netdev_egress(). [ Updated to cache the nf_get_nf_dup_skb_recursion pointer. --pablo ] Fixes: f87b9464d152 ("netfilter: nft_fwd_netdev: Support egress hook") Reported-by: Xiang Mei <xmei5@asu.edu> Signed-off-by: Weiming Shi <bestswngs@gmail.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-04-21netfilter: nf_tables: add hook transactions for device deletionsPablo Neira Ayuso1-0/+13
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 <xmei5@asu.edu> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-04-10netfilter: conntrack: remove UDP-Lite conntrack supportFernando Fernandez Mancera2-10/+0
UDP-Lite (RFC 3828) socket support was recently retired from the core networking stack. As a follow-up of that, drop the connection tracker and NAT support for UDP-Lite in Netfilter. This patch removes CONFIG_NF_CT_PROTO_UDPLITE and scrubs UDP-Lite awareness from the conntrack core, NAT core, nft_ct, and ctnetlink. Please note that stateless packet inspection, matching, ipsets or logging support for IPPROTO_UDPLITE is preserved. As conntrack no longer extracts UDP-Lite ports or tracks its L4 state, when performing NAT the UDP-Lite checksum cannot be updated anymore. That is an expected and acceptable consequence of removing UDP-Lite conntrack module. Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-04-09Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski2-1/+1
Cross-merge networking fixes after downstream PR (net-7.0-rc8). Conflicts: net/ipv6/seg6_iptunnel.c c3812651b522f ("seg6: separate dst_cache for input and output paths in seg6 lwtunnel") 78723a62b969a ("seg6: add per-route tunnel source address") https://lore.kernel.org/adZhwtOYfo-0ImSa@sirena.org.uk net/ipv4/icmp.c fde29fd934932 ("ipv4: icmp: fix null-ptr-deref in icmp_build_probe()") d98adfbdd5c01 ("ipv4: drop ipv6_stub usage and use direct function calls") https://lore.kernel.org/adO3dccqnr6j-BL9@sirena.org.uk Adjacent changes: drivers/net/ethernet/stmicro/stmmac/chain_mode.c 51f4e090b9f8 ("net: stmmac: fix integer underflow in chain mode") 6b4286e05508 ("net: stmmac: rename STMMAC_GET_ENTRY() -> STMMAC_NEXT_ENTRY()") Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-04-08netfilter: nfnetlink_queue: make hash table per queueFlorian Westphal1-1/+0
Sharing a global hash table among all queues is tempting, but it can cause crash: BUG: KASAN: slab-use-after-free in nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue] [..] nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue] nfnetlink_rcv_msg+0x46a/0x930 kmem_cache_alloc_node_noprof+0x11e/0x450 struct nf_queue_entry is freed via kfree, but parallel cpu can still encounter such an nf_queue_entry when walking the list. Alternative fix is to free the nf_queue_entry via kfree_rcu() instead, but as we have to alloc/free for each skb this will cause more mem pressure. Cc: Scott Mitchell <scott.k.mitch1@gmail.com> Fixes: e19079adcd26 ("netfilter: nfnetlink_queue: optimize verdict lookup with hash table") Signed-off-by: Florian Westphal <fw@strlen.de>
2026-04-08netfilter: nft_ct: fix use-after-free in timeout object destroyTuan Do1-0/+1
nft_ct_timeout_obj_destroy() frees the timeout object with kfree() immediately after nf_ct_untimeout(), without waiting for an RCU grace period. Concurrent packet processing on other CPUs may still hold RCU-protected references to the timeout object obtained via rcu_dereference() in nf_ct_timeout_data(). Add an rcu_head to struct nf_ct_timeout and use kfree_rcu() to defer freeing until after an RCU grace period, matching the approach already used in nfnetlink_cttimeout.c. KASAN report: BUG: KASAN: slab-use-after-free in nf_conntrack_tcp_packet+0x1381/0x29d0 Read of size 4 at addr ffff8881035fe19c by task exploit/80 Call Trace: nf_conntrack_tcp_packet+0x1381/0x29d0 nf_conntrack_in+0x612/0x8b0 nf_hook_slow+0x70/0x100 __ip_local_out+0x1b2/0x210 tcp_sendmsg_locked+0x722/0x1580 __sys_sendto+0x2d8/0x320 Allocated by task 75: nft_ct_timeout_obj_init+0xf6/0x290 nft_obj_init+0x107/0x1b0 nf_tables_newobj+0x680/0x9c0 nfnetlink_rcv_batch+0xc29/0xe00 Freed by task 26: nft_obj_destroy+0x3f/0xa0 nf_tables_trans_destroy_work+0x51c/0x5c0 process_one_work+0x2c4/0x5a0 Fixes: 7e0b2b57f01d ("netfilter: nft_ct: add ct timeout support") Cc: stable@vger.kernel.org Signed-off-by: Tuan Do <tuan@calif.io> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-04-08netfilter: nf_tables_offload: add nft_flow_action_entry_next() and use itPablo Neira Ayuso1-0/+10
Add a new helper function to retrieve the next action entry in flow rule, check if the maximum number of actions is reached, bail out in such case. Replace existing opencoded iteration on the action array by this helper function. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-04-08netfilter: nft_meta: add double-tagged vlan and pppoe supportPablo Neira Ayuso3-10/+27
Currently: add rule netdev x y ip saddr 1.1.1.1 does not work with neither double-tagged vlan nor pppoe packets. This is because the network and transport header offset are not pointing to the IP and transport protocol headers in the stack. This patch expands NFT_META_PROTOCOL and NFT_META_L4PROTO to parse double-tagged vlan and pppoe packets so matching network and transport header fields becomes possible with the existing userspace generated bytecode. Note that this parser only supports double-tagged vlan which is composed of vlan offload + vlan header in the skb payload area for simplicity. NFT_META_PROTOCOL is used by bridge and netdev family as an implicit dependency in the bytecode to match on network header fields. Similarly, there is also NFT_META_L4PROTO, which is also used as an implicit dependency when matching on the transport protocol header fields. Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-03-26Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski2-2/+23
Cross-merge networking fixes after downstream PR (net-7.0-rc6). No conflicts, or adjacent changes. Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-03-26netfilter: nf_conntrack_expect: store netns and zone in expectationPablo Neira Ayuso1-1/+17
__nf_ct_expect_find() and nf_ct_expect_find_get() are called under rcu_read_lock() but they dereference the master conntrack via exp->master. Since the expectation does not hold a reference on the master conntrack, this could be dying conntrack or different recycled conntrack than the real master due to SLAB_TYPESAFE_RCU. Store the netns, the master_tuple and the zone in struct nf_conntrack_expect as a safety measure. This patch is required by the follow up fix not to dump expectations that do not belong to this netns. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-03-26netfilter: ctnetlink: ensure safe access to master conntrackPablo Neira Ayuso1-0/+5
Holding reference on the expectation is not sufficient, the master conntrack object can just go away, making exp->master invalid. To access exp->master safely: - Grab the nf_conntrack_expect_lock, this gets serialized with clean_from_lists() which also holds this lock when the master conntrack goes away. - Hold reference on master conntrack via nf_conntrack_find_get(). Not so easy since the master tuple to look up for the master conntrack is not available in the existing problematic paths. This patch goes for extending the nf_conntrack_expect_lock section to address this issue for simplicity, in the cases that are described below this is just slightly extending the lock section. The add expectation command already holds a reference to the master conntrack from ctnetlink_create_expect(). However, the delete expectation command needs to grab the spinlock before looking up for the expectation. Expand the existing spinlock section to address this to cover the expectation lookup. Note that, the nf_ct_expect_iterate_net() calls already grabs the spinlock while iterating over the expectation table, which is correct. The get expectation command needs to grab the spinlock to ensure master conntrack does not go away. This also expands the existing spinlock section to cover the expectation lookup too. I needed to move the netlink skb allocation out of the spinlock to keep it GFP_KERNEL. For the expectation events, the IPEXP_DESTROY event is already delivered under the spinlock, just move the delivery of IPEXP_NEW under the spinlock too because the master conntrack event cache is reached through exp->master. While at it, add lockdep notations to help identify what codepaths need to grab the spinlock. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-03-26netfilter: nf_conntrack_expect: honor expectation helper fieldPablo Neira Ayuso1-1/+1
The expectation helper field is mostly unused. As a result, the netfilter codebase relies on accessing the helper through exp->master. Always set on the expectation helper field so it can be used to reach the helper. nf_ct_expect_init() is called from packet path where the skb owns the ct object, therefore accessing exp->master for the newly created expectation is safe. This saves a lot of updates in all callsites to pass the ct object as parameter to nf_ct_expect_init(). This is a preparation patches for follow up fixes. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-03-19Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski1-4/+2
Cross-merge networking fixes after downstream PR (net-7.0-rc5). net/netfilter/nft_set_rbtree.c 598adea720b97 ("netfilter: revert nft_set_rbtree: validate open interval overlap") 3aea466a43998 ("netfilter: nft_set_rbtree: don't disable bh when acquiring tree lock") https://lore.kernel.org/abgaQBpeGstdN4oq@sirena.org.uk No adjacent changes. Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-03-13nf_tables: nft_dynset: fix possible stateful expression memleak in error pathPablo Neira Ayuso1-0/+2
If cloning the second stateful expression in the element via GFP_ATOMIC fails, then the first stateful expression remains in place without being released.   unreferenced object (percpu) 0x607b97e9cab8 (size 16):     comm "softirq", pid 0, jiffies 4294931867     hex dump (first 16 bytes on cpu 3):       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00     backtrace (crc 0):       pcpu_alloc_noprof+0x453/0xd80       nft_counter_clone+0x9c/0x190 [nf_tables]       nft_expr_clone+0x8f/0x1b0 [nf_tables]       nft_dynset_new+0x2cb/0x5f0 [nf_tables]       nft_rhash_update+0x236/0x11c0 [nf_tables]       nft_dynset_eval+0x11f/0x670 [nf_tables]       nft_do_chain+0x253/0x1700 [nf_tables]       nft_do_chain_ipv4+0x18d/0x270 [nf_tables]       nf_hook_slow+0xaa/0x1e0       ip_local_deliver+0x209/0x330 Fixes: 563125a73ac3 ("netfilter: nftables: generalize set extension to support for several expressions") Reported-by: Gurpreet Shergill <giki.shergill@proton.me> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-03-13netfilter: revert nft_set_rbtree: validate open interval overlapFlorian Westphal1-4/+0
This reverts commit 648946966a08 ("netfilter: nft_set_rbtree: validate open interval overlap"). There have been reports of nft failing to laod valid rulesets after this patch was merged into -stable. I can reproduce several such problem with recent nft versions, including nft 1.1.6 which is widely shipped by distributions. We currently have little choice here. This commit can be resurrected at some point once the nftables fix that triggers the false overlap positive has appeared in common distros (see e83e32c8d1cd ("mnl: restore create element command with large batches" in nftables.git). Fixes: 648946966a08 ("netfilter: nft_set_rbtree: validate open interval overlap") Acked-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Florian Westphal <fw@strlen.de>
2026-03-05Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/netJakub Kicinski1-0/+7
Cross-merge networking fixes after downstream PR (net-7.0-rc3). No conflicts. Adjacent changes: net/netfilter/nft_set_rbtree.c fb7fb4016300 ("netfilter: nf_tables: clone set on flush only") 3aea466a4399 ("netfilter: nft_set_rbtree: don't disable bh when acquiring tree lock") Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2026-03-05netfilter: nft_set_pipapo: split gc into unlink and reclaim phaseFlorian Westphal1-0/+5
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 <yimingqian591@gmail.com> Signed-off-by: Florian Westphal <fw@strlen.de>