kernel/linux.git/net/bridge, branch v6.18.33

net: bridge: use a stable FDB dst snapshot in RCU readers

2026-05-07T04:11:45+00:00

commit df4601653201de21b487c3e7fffd464790cab808 upstream. Local FDB entries can be rewritten in place by `fdb_delete_local()`, which updates `f->dst` to another port or to `NULL` while keeping the entry alive. Several bridge RCU readers inspect `f->dst`, including `br_fdb_fillbuf()` through the `brforward_read()` sysfs path. These readers currently load `f->dst` multiple times and can therefore observe inconsistent values across the check and later dereference. In `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change `f->dst` after the NULL check and before the `port_no` dereference, leading to a NULL-ptr-deref. Fix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each affected RCU reader and using that snapshot for the rest of the access sequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()` with `WRITE_ONCE()` so the readers and writer use matching access patterns. Fixes: 960b589f86c7 ("bridge: Properly check if local fdb entry can be deleted in br_fdb_change_mac_address") Cc: stable@kernel.org Reported-by: Yifan Wu Reported-by: Juefei Pu Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Tested-by: Ren Wei Signed-off-by: Zhengchuan Liang Signed-off-by: Ren Wei Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/6570fabb85ecadb8baaf019efe856f407711c7b9.1776043229.git.zcliangcn@gmail.com Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman

bridge: guard local VLAN-0 FDB helpers against NULL vlan group

2026-04-22T11:22:19+00:00

[ Upstream commit 1979645e1842cb7017525a61a0e0e0beb924d02a ] When CONFIG_BRIDGE_VLAN_FILTERING is not set, br_vlan_group() and nbp_vlan_group() return NULL (br_private.h stub definitions). The BR_BOOLOPT_FDB_LOCAL_VLAN_0 toggle code is compiled unconditionally and reaches br_fdb_delete_locals_per_vlan_port() and br_fdb_insert_locals_per_vlan_port(), where the NULL vlan group pointer is dereferenced via list_for_each_entry(v, &vg->vlan_list, vlist). The observed crash is in the delete path, triggered when creating a bridge with IFLA_BR_MULTI_BOOLOPT containing BR_BOOLOPT_FDB_LOCAL_VLAN_0 via RTM_NEWLINK. The insert helper has the same bug pattern. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000056: 0000 [#1] KASAN NOPTI KASAN: null-ptr-deref in range [0x00000000000002b0-0x00000000000002b7] RIP: 0010:br_fdb_delete_locals_per_vlan+0x2b9/0x310 Call Trace: br_fdb_toggle_local_vlan_0+0x452/0x4c0 br_toggle_fdb_local_vlan_0+0x31/0x80 net/bridge/br.c:276 br_boolopt_toggle net/bridge/br.c:313 br_boolopt_multi_toggle net/bridge/br.c:364 br_changelink net/bridge/br_netlink.c:1542 br_dev_newlink net/bridge/br_netlink.c:1575 Add NULL checks for the vlan group pointer in both helpers, returning early when there are no VLANs to iterate. This matches the existing pattern used by other bridge FDB functions such as br_fdb_add() and br_fdb_delete(). Fixes: 21446c06b441 ("net: bridge: Introduce UAPI for BR_BOOLOPT_FDB_LOCAL_VLAN_0") Signed-off-by: Zijing Yin Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260402140153.3925663-1-yzjaurora@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bridge: br_nd_send: validate ND option lengths

2026-04-11T12:26:43+00:00

commit 850837965af15707fd3142c1cf3c5bfaf022299b upstream. br_nd_send() walks ND options according to option-provided lengths. A malformed option can make the parser advance beyond the computed option span or use a too-short source LLADDR option payload. Validate option lengths against the remaining NS option area before advancing, and only read source LLADDR when the option is large enough for an Ethernet address. Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports") Cc: stable@vger.kernel.org Reported-by: Yifan Wu Reported-by: Juefei Pu Tested-by: Ao Zhou Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Signed-off-by: Yang Yang Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260326034441.2037420-3-n05ec@lzu.edu.cn Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

bridge: br_nd_send: linearize skb before parsing ND options

2026-04-11T12:26:21+00:00

[ Upstream commit a01aee7cafc575bb82f5529e8734e7052f9b16ea ] br_nd_send() parses neighbour discovery options from ns->opt[] and assumes that these options are in the linear part of request. Its callers only guarantee that the ICMPv6 header and target address are available, so the option area can still be non-linear. Parsing ns->opt[] in that case can access data past the linear buffer. Linearize request before option parsing and derive ns from the linear network header. Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports") Reported-by: Yifan Wu Reported-by: Juefei Pu Tested-by: Ao Zhou Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Signed-off-by: Yang Yang Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260326034441.2037420-2-n05ec@lzu.edu.cn Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bridge: cfm: Fix race condition in peer_mep deletion

2026-03-25T10:10:40+00:00

[ Upstream commit 3715a00855316066cdda69d43648336367422127 ] When a peer MEP is being deleted, cancel_delayed_work_sync() is called on ccm_rx_dwork before freeing. However, br_cfm_frame_rx() runs in softirq context under rcu_read_lock (without RTNL) and can re-schedule ccm_rx_dwork via ccm_rx_timer_start() between cancel_delayed_work_sync() returning and kfree_rcu() being called. The following is a simple race scenario: cpu0 cpu1 mep_delete_implementation() cancel_delayed_work_sync(ccm_rx_dwork); br_cfm_frame_rx() // peer_mep still in hlist if (peer_mep->ccm_defect) ccm_rx_timer_start() queue_delayed_work(ccm_rx_dwork) hlist_del_rcu(&peer_mep->head); kfree_rcu(peer_mep, rcu); ccm_rx_work_expired() // on freed peer_mep To prevent this, cancel_delayed_work_sync() is replaced with disable_delayed_work_sync() in both peer MEP deletion paths, so that subsequent queue_delayed_work() calls from br_cfm_frame_rx() are silently rejected. The cc_peer_disable() helper retains cancel_delayed_work_sync() because it is also used for the CC enable/disable toggle path where the work must remain re-schedulable. Fixes: dc32cbb3dbd7 ("bridge: cfm: Kernel space implementation of CFM. CCM frame RX added.") Signed-off-by: Hyunwoo Kim Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/abBgYT5K_FI9rD1a@v4bel Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled

2026-03-12T11:10:00+00:00

[ Upstream commit e5e890630533bdc15b26a34bb8e7ef539bdf1322 ] When booting with the 'ipv6.disable=1' parameter, the nd_tbl is never initialized because inet6_init() exits before ndisc_init() is called which initializes it. Then, if neigh_suppress is enabled and an ICMPv6 Neighbor Discovery packet reaches the bridge, br_do_suppress_nd() will dereference ipv6_stub->nd_tbl which is NULL, passing it to neigh_lookup(). This causes a kernel NULL pointer dereference. BUG: kernel NULL pointer dereference, address: 0000000000000268 Oops: 0000 [#1] PREEMPT SMP NOPTI [...] RIP: 0010:neigh_lookup+0x16/0xe0 [...] Call Trace: ? neigh_lookup+0x16/0xe0 br_do_suppress_nd+0x160/0x290 [bridge] br_handle_frame_finish+0x500/0x620 [bridge] br_handle_frame+0x353/0x440 [bridge] __netif_receive_skb_core.constprop.0+0x298/0x1110 __netif_receive_skb_one_core+0x3d/0xa0 process_backlog+0xa0/0x140 __napi_poll+0x2c/0x170 net_rx_action+0x2c4/0x3a0 handle_softirqs+0xd0/0x270 do_softirq+0x3f/0x60 Fix this by replacing IS_ENABLED(IPV6) call with ipv6_mod_enabled() in the callers. This is in essence disabling NS/NA suppression when IPv6 is disabled. Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports") Reported-by: Guruprasad C P Closes: https://lore.kernel.org/netdev/CAHXs0ORzd62QOG-Fttqa2Cx_A_VFp=utE2H2VTX5nqfgs7LDxQ@mail.gmail.com/ Signed-off-by: Fernando Fernandez Mancera Reviewed-by: Ido Schimmel Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260304120357.9778-1-fmancera@suse.de Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: bridge: mcast: always update mdb_n_entries for vlan contexts

2026-02-26T22:59:39+00:00

[ Upstream commit 8b769e311a86bb9d15c5658ad283b86fc8f080a2 ] syzbot triggered a warning[1] about the number of mdb entries in a context. It turned out that there are multiple ways to trigger that warning today (some got added during the years), the root cause of the problem is that the increase is done conditionally, and over the years these different conditions increased so there were new ways to trigger the warning, that is to do a decrease which wasn't paired with a previous increase. For example one way to trigger it is with flush: $ ip l add br0 up type bridge vlan_filtering 1 mcast_snooping 1 $ ip l add dumdum up master br0 type dummy $ bridge mdb add dev br0 port dumdum grp 239.0.0.1 permanent vid 1 $ ip link set dev br0 down $ ip link set dev br0 type bridge mcast_vlan_snooping 1 ^^^^ this will enable snooping, but will not update mdb_n_entries because in __br_multicast_enable_port_ctx() we check !netif_running $ bridge mdb flush dev br0 ^^^ this will trigger the warning because it will delete the pg which we added above, which will try to decrease mdb_n_entries Fix the problem by removing the conditional increase and always keep the count up-to-date while the vlan exists. In order to do that we have to first initialize it on port-vlan context creation, and then always increase or decrease the value regardless of mcast options. To keep the current behaviour we have to enforce the mdb limit only if the context is port's or if the port-vlan's mcast snooping is enabled. [1] ------------[ cut here ]------------ n == 0 WARNING: net/bridge/br_multicast.c:718 at br_multicast_port_ngroups_dec_one net/bridge/br_multicast.c:718 [inline], CPU#0: syz.4.4607/22043 WARNING: net/bridge/br_multicast.c:718 at br_multicast_port_ngroups_dec net/bridge/br_multicast.c:771 [inline], CPU#0: syz.4.4607/22043 WARNING: net/bridge/br_multicast.c:718 at br_multicast_del_pg+0x1bbe/0x1e20 net/bridge/br_multicast.c:825, CPU#0: syz.4.4607/22043 Modules linked in: CPU: 0 UID: 0 PID: 22043 Comm: syz.4.4607 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026 RIP: 0010:br_multicast_port_ngroups_dec_one net/bridge/br_multicast.c:718 [inline] RIP: 0010:br_multicast_port_ngroups_dec net/bridge/br_multicast.c:771 [inline] RIP: 0010:br_multicast_del_pg+0x1bbe/0x1e20 net/bridge/br_multicast.c:825 Code: 41 5f 5d e9 04 7a 48 f7 e8 3f 73 5c f7 90 0f 0b 90 e9 cf fd ff ff e8 31 73 5c f7 90 0f 0b 90 e9 16 fd ff ff e8 23 73 5c f7 90 <0f> 0b 90 e9 60 fd ff ff e8 15 73 5c f7 eb 05 e8 0e 73 5c f7 48 8b RSP: 0018:ffffc9000c207220 EFLAGS: 00010293 RAX: ffffffff8a68042d RBX: ffff88807c6f1800 RCX: ffff888066e90000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffff888066e90000 R09: 000000000000000c R10: 000000000000000c R11: 0000000000000000 R12: ffff8880303ef800 R13: dffffc0000000000 R14: ffff888050eb11c4 R15: 1ffff1100a1d6238 FS: 00007fa45921b6c0(0000) GS:ffff8881256f5000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa4591f9ff8 CR3: 0000000081df2000 CR4: 00000000003526f0 Call Trace: br_mdb_flush_pgs net/bridge/br_mdb.c:1525 [inline] br_mdb_flush net/bridge/br_mdb.c:1544 [inline] br_mdb_del_bulk+0x5e2/0xb20 net/bridge/br_mdb.c:1561 rtnl_mdb_del+0x48a/0x640 net/core/rtnetlink.c:-1 rtnetlink_rcv_msg+0x77e/0xbe0 net/core/rtnetlink.c:6967 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646 __sys_sendmsg net/socket.c:2678 [inline] __do_sys_sendmsg net/socket.c:2683 [inline] __se_sys_sendmsg net/socket.c:2681 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa45839aeb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa45921b028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fa458615fa0 RCX: 00007fa45839aeb9 RDX: 0000000000000000 RSI: 00002000000000c0 RDI: 0000000000000004 RBP: 00007fa458408c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa458616038 R14: 00007fa458615fa0 R15: 00007fff0b59fae8 Fixes: b57e8d870d52 ("net: bridge: Maintain number of MDB entries in net_bridge_mcast_port") Reported-by: syzbot+d5d1b7343531d17bd3c5@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/aYrWbRp83MQR1ife@debil/T/#t Reviewed-by: Ido Schimmel Signed-off-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260213070031.1400003-2-nikolay@nvidia.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

netfilter: replace -EEXIST with -EBUSY

2026-02-11T12:41:49+00:00

[ Upstream commit 2bafeb8d2f380c3a81d98bd7b78b854b564f9cd4 ] The -EEXIST error code is reserved by the module loading infrastructure to indicate that a module is already loaded. When a module's init function returns -EEXIST, userspace tools like kmod interpret this as "module already loaded" and treat the operation as successful, returning 0 to the user even though the module initialization actually failed. Replace -EEXIST with -EBUSY to ensure correct error reporting in the module initialization path. Affected modules: * ebtable_broute ebtable_filter ebtable_nat arptable_filter * ip6table_filter ip6table_mangle ip6table_nat ip6table_raw * ip6table_security iptable_filter iptable_mangle iptable_nat * iptable_raw iptable_security Signed-off-by: Daniel Gomez Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin

net: bridge: fix static key check

2026-02-06T15:57:33+00:00

[ Upstream commit cc0cf10fdaeadf5542d64a55b5b4120d3df90b7d ] Fix the check if netfilter's static keys are available. netfilter defines and exports static keys if CONFIG_JUMP_LABEL is enabled. (HAVE_JUMP_LABEL is never defined.) Fixes: 971502d77faa ("bridge: netfilter: unroll NF_HOOK helper in bridge input path") Signed-off-by: Martin Kaiser Reviewed-by: Florian Westphal Reviewed-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260127101925.1754425-1-martin@kaiser.cx Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: bridge: annotate data-races around fdb->{updated,used}

2026-01-23T10:21:16+00:00

[ Upstream commit b25a0b4a2193407aa72a4cd1df66a7ed07dd4f1e ] fdb->updated and fdb->used are read and written locklessly. Add READ_ONCE()/WRITE_ONCE() annotations. Fixes: 31cbc39b6344 ("net: bridge: add option to allow activity notifications for any fdb entries") Reported-by: syzbot+bfab43087ad57222ce96@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/695e3d74.050a0220.1c677c.035f.GAE@google.com/ Signed-off-by: Eric Dumazet Acked-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260108093806.834459-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin