wireguard-linux/net/bridge, branch stable

net: bridge: avoid recursive multicast port cleanup

2026-10-05T02:29:53Z

br_multicast_sg_del_exclude_ports() removes automatically added STAR_EXCL port groups by calling br_multicast_del_pg(). For S,G entries, that deletion calls back into br_multicast_sg_del_exclude_ports(), so a large number of STAR_EXCL ports consumes one kernel stack frame per port and can hit the stack guard page. Keep the complete port-group deletion path for cleanup, but suppress the S,G exclude-port cleanup while that helper is already walking the same entry. Normal deletion callers retain the existing behavior. Fixes: 8266a0491e92 ("net: bridge: mcast: handle port group filter modes") Cc: stable@vger.kernel.org Reported-by: Vega Assisted-by: LLM Signed-off-by: Zixuan Chai Signed-off-by: Ren Wei Signed-off-by: David S. Miller

bridge: check llc_mac_hdr_init() return value in br_send_bpdu()

2026-09-24T18:00:59Z

If llc_mac_hdr_init() fails (for instance if the port device type does not support LLC or dev_hard_header() fails), br_send_bpdu() should drop the skb instead of resetting the mac header to the LLC payload and transmitting a malformed frame. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Closes: https://lore.kernel.org/netdev/179022851638.2160803.1808206741379444999@kernel.org/ Cc: Nikolay Aleksandrov Cc: Ido Schimmel Cc: bridge@lists.linux.dev Signed-off-by: Eric Dumazet Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260924082951.1599377-3-edumazet@google.com Signed-off-by: Jakub Kicinski

net: bridge: mdb: restart port group walk after deletion

2026-09-23T23:51:03Z

br_mdb_flush_pgs() keeps a pointer-to-pointer cursor while walking mp->ports. br_multicast_del_pg() can re-enter the same MDB entry through br_multicast_sg_del_exclude_ports() and unlink other port groups. If the cursor points into one of those groups, the next iteration dereferences a stale cursor and can leave mp->ports pointing at freed memory. A following RTM_GETMDB exposes the dangling pointer: BUG: KASAN: slab-use-after-free in br_mdb_dump Read of size 8 br_mdb_dump rtnl_mdb_dump rtnl_dumpit netlink_dump Reset the cursor to mp->ports after every deletion. The deletion removes at least the selected group, so the restarted walk always makes progress. Fixes: a6acb535afb2 ("bridge: mdb: Add MDB bulk deletion support") Cc: stable@vger.kernel.org Signed-off-by: Fourie Zhang Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260920110852.60293-1-fouriezhang@tencent.com Signed-off-by: Jakub Kicinski

net: bridge: vlan: fix bugs caused by switchdev deletion errors

2026-09-16T01:31:57Z

Allowing switchdev to prevent vlan deletion and error out in __vlan_del could cause multiple different issues - inconsistent state, memory leaks when flushing, NULL pointer dereference on bridge error when flushing. It doesn't make sense to allow it to stop __vlan_del, so log the error and continue with software vlan deletion. This is also consistent with 8021q behaviour. Suggested-by: Ido Schimmel Fixes: bf361ad38165 ("net: bridge: check __vlan_vid_del for error") Fixes: 5454f5c28eca ("net: bridge: vlan: check for errors from __vlan_del in __vlan_flush") Fixes: 2594e9064a57 ("bridge: vlan: add per-vlan struct and move to rhashtables") Fixes: 9c86ce2c1ae3 ("net: bridge: Notify about bridge VLANs") Signed-off-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260914105258.3436918-1-razor@blackwall.org Signed-off-by: Jakub Kicinski

net: bridge: mst: move switchdev call outside rcu

2026-09-15T10:27:41Z

This is a follow-up of one of sashiko's pre-existing bug reports. br_mst_set_state() calls switchdev_port_attr_set() for nonzero MSTIs while holding rcu_read_lock() which invokes the blocking switchdev notifier chain and may sleep. Nonzero MSTI changes come from netlink with rtnl held. Move the switchdev call before entering the rcu section and assert that rtnl is held. The call cannot be deferred because netlink needs its error and extack. Also DSA reads the old bridge MST state during the callback and checks it. A deferred callback will be late and will see the updated state. Fixes: 3a7c1661ae13 ("net: bridge: mst: fix vlan use-after-free") Signed-off-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260911105021.1385934-1-razor@blackwall.org Signed-off-by: Paolo Abeni

net: bridge: use option bits for CFM/MRP frame handlers

2026-09-09T00:48:49Z

CFM and MRP register a global br_frame_type whose hlist_node is linked into the per-bridge frame_type_list when the first MEP/MRP instance is created. Enabling the protocol on multiple bridges therefore inserts the same node into multiple lists. Unregistering it on one bridge then corrupts list state belonging to another. These handlers can only be installed once per bridge, and they are uncommon. Track their per-bridge enable state with net_bridge option bits, which already live on the Rx hot cache line, and dispatch the matching handler directly from the receive path. Check both bits together first as an unlikely case. Remove the generic frame_type_list and br_frame_type helpers, which have had no other users since CFM and MRP were added. That shrinks struct net_bridge by 8 bytes and drops the list walk from the fast path. When neither protocol is compiled in, BR_CFM_MRP_OPTS is 0 and the compiler prunes the branch. Fixes: 90c628dd47ff ("net: bridge: extend the process of special frames") Fixes: dc32cbb3dbd7 ("bridge: cfm: Kernel space implementation of CFM. CCM frame RX added.") Cc: stable@vger.kernel.org Reported-by: Vega Suggested-by: Nikolay Aleksandrov Co-developed-by: Yilin Zhu Signed-off-by: Yilin Zhu Signed-off-by: Zhiling Zou Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/0345b9d5aa60ba416f6738ff1b87140f0a749cb8.1788417901.git.zhilinz@nebusec.ai Signed-off-by: Jakub Kicinski

net: bridge: mcast: properly convert mglist to rcu

2026-09-04T22:29:47Z

Sashiko reported a bug [1] that br_multicast_del_port_group unlists the port group not using proper rcu helper that preserves the next pointer and after that immediately frees the port group without waiting for rcu grace period. The only rcu walker of mglist is br_multicast_list_adjacent() and it turns out that function has always been buggy because mglist was never properly converted to RCU. Fix it by converting it to rcu and moving its initialization after eth_addr's. Initializing p->next can use RCU_INIT_POINTER because we have a barrier from the hlist_add_head_rcu call later, besides we're initializing an unpublished structure anyway. [1] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260826014200.362304-1-littleddfu%40gmail.com Fixes: 07f8ac4a1e26 ("bridge: add export of multicast database adjacent to net_dev") Signed-off-by: Nikolay Aleksandrov Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260903093851.1494297-1-razor@blackwall.org Signed-off-by: Jakub Kicinski

net: bridge: mcast: don't truncate the port group walk on teardown

2026-09-03T01:25:35Z

__br_multicast_disable_port_ctx() and br_multicast_del_port() walk port->mglist with hlist_for_each_entry_safe(). However, br_multicast_find_del_pg() can also delete other entries from the same list through br_multicast_fwd_src_remove() or __fwd_del_star_excl(). If such an entry is the iterator's saved next node, hlist_del_init() clears its ->next and terminates the walk early. The reproducer triggers this in both teardown walks, leaving port groups in the bridge mdb with a dangling ->key.port after del_nbp() frees the port: BUG: KASAN: slab-use-after-free in __mdb_fill_info+0x1191/0x1320 __mdb_fill_info+0x1191/0x1320 br_mdb_dump+0x594/0xe40 rtnl_mdb_dump+0x1cf/0x5d0 Use hlist_del_init_rcu() to unlink the group while preserving ->next. br_multicast_del_pg() and the teardown walks run under br->multicast_lock. The GC worker must acquire the same lock before detaching the group for destruction, so the node remains alive while the walk uses the preserved pointer. Preserving ->next means a walk can now reach a group that an earlier iteration already deleted as a side effect. That group is off mp->ports, so br_multicast_find_del_pg() would fall through its port scan and hit the trailing WARN_ON(1). Skip such groups at the top of that helper: a port group is put on port->mglist when it is created and only unlinked when it is deleted, so hlist_unhashed() identifies exactly this case. Fixes: b08123684bd5 ("net: bridge: mcast: install S,G entries automatically based on reports") Cc: stable@vger.kernel.org Suggested-by: Nikolay Aleksandrov Reported-by: TencentOS Corvus AI Signed-off-by: Jun Yang Reviewed-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260831111330.199543-1-junvyyang@tencent.com Signed-off-by: Jakub Kicinski

net: bridge: mcast: fix use-after-free of a master VLAN's multicast context

2026-08-27T19:35:03Z

br_multicast_toggle_one_vlan() clears BR_VLFLAG_MCAST_ENABLED under br->multicast_lock before stopping a VLAN's multicast context. That is the teardown handshake: lockless readers gate on the flag through br_multicast_ctx_should_use() -> br_multicast_ctx_vlan_disabled(), so once it is cleared under the lock no reader can arm the context again. For a master VLAN the handshake never runs. __vlan_del() clears BRIDGE_VLAN_INFO_BRENTRY before calling br_vlan_put_master(), so br_multicast_toggle_one_vlan(masterv, false) returns early on !br_vlan_is_brentry(vlan): the flag stays set and br->multicast_lock is never taken. br_vlan_put_master() then drains the context in br_multicast_ctx_deinit() and frees the VLAN through call_rcu(), while a reader still inside rcu_read_lock() sees the context as enabled and re-arms it. The port and port-VLAN branch of the function has no br_vlan_is_brentry() test and flips the flag under br->multicast_lock, so it is not affected. The reader is the bridge transmit path. For a master VLAN br_multicast_rcv() selects brmctx = &vlan->br_mcast_ctx with pmctx = NULL, so IGMP sent to the bridge device re-arms the context's timers after br_multicast_ctx_deinit() has already stopped them. BUG: KASAN: slab-use-after-free in detach_if_pending+0x412/0x4a0 Write of size 8 at addr ffff88810ac39918 by task brmc/601 __mod_timer+0x51a/0xc50 br_multicast_host_join+0x25b/0x390 __br_multicast_add_group+0x468/0x530 br_ip4_multicast_add_group+0x1a0/0x260 br_multicast_rcv+0x2cda/0x61e0 br_dev_xmit+0x6c4/0x1540 Allocated by task 610: br_vlan_add+0x111/0xb40 br_vlan_info+0x370/0x3e0 Freed by task 0: kfree+0x1a7/0x4f0 rcu_core+0x7dc/0x10a0 Only test br_vlan_is_brentry() when enabling, like the br_multicast_ctx_vlan_global_disabled() test next to it. Disabling then always clears BR_VLFLAG_MCAST_ENABLED under br->multicast_lock before br_multicast_ctx_deinit() drains the context. Fixes: 7b54aaaf53cb ("net: bridge: multicast: add vlan state initialization and control") Cc: stable@vger.kernel.org Signed-off-by: Norbert Szetei Acked-by: Nikolay Aleksandrov Link: https://patch.msgid.link/D400F6C7-543A-4B79-9E5B-D1D8974DE5C9@doyensec.com Signed-off-by: Jakub Kicinski

net: bridge: arp/nd proxy: fix reading neigh ha

2026-08-20T21:23:06Z

Currently neigh ha address is read directly, but that can result in torn/partial reads if the neigh is being updated. Use neigh_ha_snapshot to take a stable snapshot of the address. Fixes: 057658cb33fb ("bridge: suppress arp pkts on BR_NEIGH_SUPPRESS ports") Fixes: ed842faeb2bd ("bridge: suppress nd pkts on BR_NEIGH_SUPPRESS ports") Signed-off-by: Nikolay Aleksandrov Reviewed-by: Petr Machata Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260818150756.890025-2-razor@blackwall.org Signed-off-by: Jakub Kicinski