linux.git/net/bridge, branch v7.1-rc5

net: bridge: prevent too big nested attributes in br_fill_linkxstats()

2026-05-21T15:47:36+00:00

After commit ff205bf8c554 ("netlink: add one debug check in nla_nest_end()")
syzbot found that br_fill_linkxstats() can send corrupted netlink packets.

Make sure the nested attribute size is bounded.

Fixes: a60c090361ea ("bridge: netlink: export per-vlan stats")
Reported-by: syzbot+a35f9259d08f907c06e6@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a0b0da3.050a0220.175f0c.0000.GAE@google.com/
Signed-off-by: Eric Dumazet 
Reviewed-by: Ido Schimmel 
Acked-by: Nikolay Aleksandrov 
Link: https://patch.msgid.link/20260520114207.1394241-1-edumazet@google.com
Signed-off-by: Jakub Kicinski

bridge: mcast: Fix a possible use-after-free when removing a bridge port

2026-05-20T01:15:22+00:00

When per-VLAN multicast snooping is enabled, the bridge iterates over
all the bridge ports, disables the per-port multicast context on each
port and enables the per-{port, VLAN} multicast contexts instead. The
reverse happens when per-VLAN multicast snooping is disabled.

When global multicast snooping is enabled, the bridge iterates over all
the bridge ports and enables the per-port multicast context on each
port. The reverse happens when multicast snooping is disabled.

The above scheme can result in a situation where both types of contexts
(per-port and per-{port, VLAN}) are enabled on a single bridge port:

 # ip link add name br1 up type bridge mcast_snooping 1 mcast_querier 1 vlan_filtering 1
 # ip link add name dummy1 up master br1 type dummy
 # ip link set dev br1 type bridge mcast_vlan_snooping 1
 # ip link set dev br1 type bridge mcast_snooping 0
 # ip link set dev br1 type bridge mcast_snooping 1

This is not intended and it is a problem since the commit cited below.
Prior to this commit, when removing a bridge port,
br_multicast_disable_port() would disable the per-port multicast context
and the per-{port, VLAN} multicast contexts would get disabled when
flushing VLANs.

After this commit, br_multicast_disable_port() only disables the
per-port multicast context if per-VLAN multicast snooping is disabled.
If both types of contexts were enabled on the port when it was removed,
the per-port multicast context would remain enabled when freeing the
bridge port, leading to a use-after-free [1].

Fix by preventing the bridge from enabling / disabling the per-port
multicast contexts when toggling global multicast snooping if per-VLAN
multicast snooping is enabled.

[1]
ODEBUG: free active (active state 0) object: ffff88810f8bda78 object type: timer_list hint: br_ip6_multicast_port_query_expired (net/bridge/br_multicast.c:1927)
WARNING: lib/debugobjects.c:629 at debug_print_object+0x1b1/0x3e0, CPU#5: swapper/5/0
[...]
Call Trace:

__debug_check_no_obj_freed (lib/debugobjects.c:1116)
kfree (mm/slub.c:2620 mm/slub.c:6250 mm/slub.c:6565)
kobject_cleanup (lib/kobject.c:689)
rcu_do_batch (kernel/rcu/tree.c:2617)
rcu_core (kernel/rcu/tree.c:2869)
handle_softirqs (kernel/softirq.c:622)
__irq_exit_rcu (kernel/softirq.c:656 kernel/softirq.c:496 kernel/softirq.c:735)
irq_exit_rcu (kernel/softirq.c:752)
sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1061 (discriminator 47) arch/x86/kernel/apic/apic.c:1061 (discriminator 47))


Fixes: 4b30ae9adb04 ("net: bridge: mcast: re-implement br_multicast_{enable, disable}_port functions")
Reported-by: syzbot+ae231e0552fa77b26ea1@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/87qznowlfs.ffs@tglx/
Reported-by: Thomas Gleixner 
Acked-by: Nikolay Aleksandrov 
Signed-off-by: Ido Schimmel 
Link: https://patch.msgid.link/20260517121122.188333-2-idosch@nvidia.com
Signed-off-by: Jakub Kicinski

netfilter: br_netfilter: Reallocate headroom if necessary in neigh_hh_bridge()

2026-05-16T11:22:50+00:00

neigh_hh_bridge() assumes the skb always has sufficient headroom to copy
the aligned  L2 header. This assumption can trigger the crash reported
below using the following netfilter setup:

$modprobe br_netfilter
$sysctl -w net.bridge.bridge-nf-call-iptables=1

$root@OpenWrt:~# nft list ruleset
table ip nat {
        chain prerouting {
                type nat hook prerouting priority dstnat; policy accept;
                ip daddr 192.168.83.123 dnat to 192.168.83.120
        }
}

- iperf3 client (192.168.83.119) --> bridge (192.168.83.118) --> iperf3 server (192.168.83.120)

the iperf3 client is sending packet for 192.168.83.123 to the bridge device.

[ 1579.036575] Unable to handle kernel write to read-only memory at virtual address ffffff8004d76ffe
[ 1579.045482] Mem abort info:
[ 1579.048273]   ESR = 0x000000009600004f
[ 1579.052024]   EC = 0x25: DABT (current EL), IL = 32 bits
[ 1579.057363]   SET = 0, FnV = 0
[ 1579.060417]   EA = 0, S1PTW = 0
[ 1579.063550]   FSC = 0x0f: level 3 permission fault
[ 1579.068345] Data abort info:
[ 1579.071224]   ISV = 0, ISS = 0x0000004f, ISS2 = 0x00000000
[ 1579.076720]   CM = 0, WnR = 1, TnD = 0, TagAccess = 0
[ 1579.081770]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[ 1579.087092] swapper pgtable: 4k pages, 39-bit VAs, pgdp=0000000080dc4000
[ 1579.093794] [ffffff8004d76ffe] pgd=180000009ffff003, p4d=180000009ffff003, pud=180000009ffff003, pmd=180000009ffe3003, pte=0060000084d76787
[ 1579.106343] Internal error: Oops: 000000009600004f [#1] SMP
[ 1579.193824] CPU: 0 UID: 0 PID: 235 Comm: napi/qdma_eth-3 Tainted: G           O       6.12.57 #0
[ 1579.202614] Tainted: [O]=OOT_MODULE
[ 1579.206102] Hardware name: Airoha AN7581 Evaluation Board (DT)
[ 1579.211929] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 1579.218889] pc : br_nf_pre_routing_finish_bridge+0x1ac/0xcc8 [br_netfilter]
[ 1579.225859] lr : br_nf_pre_routing_finish_bridge+0x18c/0xcc8 [br_netfilter]
[ 1579.232822] sp : ffffffc0817cba20
[ 1579.236128] x29: ffffffc0817cba20 x28: 0000000000000000 x27: ffffff8002b89000
[ 1579.243273] x26: ffffff8004d7700e x25: 0000000000000008 x24: 0000000000000000
[ 1579.250416] x23: ffffffc08179d4c0 x22: 0000000000000000 x21: ffffffc08179d4c0
[ 1579.257561] x20: ffffff8004d9b800 x19: ffffff8015010000 x18: 0000000000000014
[ 1579.264704] x17: ffffffbf9e930000 x16: ffffffc0817c8000 x15: 0000000000000070
[ 1579.271848] x14: 0000000000000080 x13: 0000000000000001 x12: 0000000000000000
[ 1579.278993] x11: ffffffc0798caae0 x10: ffffff8014db6fd8 x9 : 0000000000000000
[ 1579.286136] x8 : 0000000000000003 x7 : ffffffc08171f628 x6 : 000000001a3b83d3
[ 1579.293281] x5 : 0000000000000000 x4 : 1beb76f22fee0000 x3 : ffffff8004d7700e
[ 1579.300425] x2 : 0000000000000000 x1 : ffffff8004d9b8bc x0 : ffffff80026ed000
[ 1579.307570] Call trace:
[ 1579.310018]  br_nf_pre_routing_finish_bridge+0x1ac/0xcc8 [br_netfilter]
[ 1579.316632]  br_nf_hook_thresh+0xd4/0x14bc [br_netfilter]
[ 1579.322032]  br_nf_hook_thresh+0x250/0x14bc [br_netfilter]
[ 1579.327517]  br_nf_hook_thresh+0x76c/0x14bc [br_netfilter]
[ 1579.333003]  br_handle_frame+0x180/0x480
[ 1579.336935]  __netif_receive_skb_core.constprop.0+0x540/0xf40
[ 1579.342682]  __netif_receive_skb_one_core+0x28/0x50
[ 1579.347561]  process_backlog+0x98/0x1e0
[ 1579.351398]  __napi_poll+0x34/0x1c4
[ 1579.354887]  net_rx_action+0x178/0x330
[ 1579.358638]  handle_softirqs+0x108/0x2d4
[ 1579.362560]  __do_softirq+0x10/0x18
[ 1579.366051]  ____do_softirq+0xc/0x20
[ 1579.369627]  call_on_irq_stack+0x30/0x4c
[ 1579.373550]  do_softirq_own_stack+0x18/0x20
[ 1579.377734]  do_softirq+0x4c/0x60
[ 1579.381050]  __local_bh_enable_ip+0x88/0x98
[ 1579.385234]  napi_threaded_poll_loop+0x188/0x21c
[ 1579.389853]  napi_threaded_poll+0x70/0x80
[ 1579.393863]  kthread+0xd8/0xdc
[ 1579.396918]  ret_from_fork+0x10/0x20
[ 1579.400499] Code: 88dffc22 3707ffc2 f9406663 f9406684 (f81f0064)
[ 1579.406589] ---[ end trace 0000000000000000 ]---
[ 1579.411209] Kernel panic - not syncing: Oops: Fatal exception in interrupt
[ 1579.418083] SMP: stopping secondary CPUs
[ 1579.422012] Kernel Offset: disabled

Fix the issue reallocating the skb headroom if necessary in neigh_hh_bridge routine.

Fixes: e179e6322ac33 ("netfilter: bridge-netfilter: Fix MAC header handling with IP DNAT")
Reviewed-by: Ido Schimmel 
Signed-off-by: Lorenzo Bianconi 
Signed-off-by: Pablo Neira Ayuso

netfilter: bridge: eb_tables: close module init race

2026-05-07T23:30:17+00:00

sashiko reports for unrelated patch:
 Does the core ebtables initialization in ebtables.c suffer from a similar race?
 Once nf_register_sockopt() completes, the sockopts are exposed globally.

sockopt has to be registered last, just like in ip/ip6/arptables.

Fixes: 5b53951cfc85 ("netfilter: ebtables: use net_generic infra")
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

netfilter: ebtables: close dangling table module init race

2026-05-07T23:30:17+00:00

sashiko reported for a related patch:
 In modules like iptable_raw.c, [..], if register_pernet_subsys() fails,
 the rollback might call kfree(rawtable_ops) before [..]
 During this window, could a concurrent userspace process find the globally
 visible template, trigger table_init(), [..]

The table init functions must always register the template last.

Otherwise, set/getsockopt can instantiate a table in a namespace
while the required pernet ops (contain the destructor) isn't available.
This change is also required in x_tables, handled in followup change.

Fixes: 87663c39f898 ("netfilter: ebtables: do not hook tables by default")
Reviewed-by: Tristan Madani 
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

netfilter: ebtables: move to two-stage removal scheme

2026-05-07T23:30:17+00:00

Like previous patches for x_tables, follow same pattern in ebtables.
We can't reuse xt helpers: ebt_table struct layout is incompatible.

table->ops assignment is now done while still holding the ebt mutex
to make sure we never expose partially-filled table struct.

Fixes: 87663c39f898 ("netfilter: ebtables: do not hook tables by default")
Reviewed-by: Tristan Madani 
Signed-off-by: Florian Westphal 
Signed-off-by: Pablo Neira Ayuso

Merge tag 'net-deletions' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

2026-04-24T16:41:58+00:00

Pull networking deletions from Jakub Kicinski:
 "Delete some obsolete networking code

  Old code like amateur radio and NFC have long been a burden to core
  networking developers. syzbot loves to find bugs in BKL-era code, and
  noobs try to fix them.

  If we want to have a fighting chance of surviving the LLM-pocalypse
  this code needs to find a dedicated owner or get deleted. We've talked
  about these deletions multiple times in the past and every time
  someone wanted the code to stay. It is never very clear to me how many
  of those people actually use the code vs are just nostalgic to see it
  go. Amateur radio did have occasional users (or so I think) but most
  users switched to user space implementations since its all super slow
  stuff. Nobody stepped up to maintain the kernel code.

  We were lucky enough to find someone who wants to help with NFC so
  we're giving that a chance. Let's try to put the rest of this code
  behind us"

* tag 'net-deletions' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next:
  drivers: net: 8390: wd80x3: Remove this driver
  drivers: net: 8390: ultra: Remove this driver
  drivers: net: 8390: AX88190: Remove this driver
  drivers: net: fujitsu: fmvj18x: Remove this driver
  drivers: net: smsc: smc91c92: Remove this driver
  drivers: net: smsc: smc9194: Remove this driver
  drivers: net: amd: nmclan: Remove this driver
  drivers: net: amd: lance: Remove this driver
  drivers: net: 3com: 3c589: Remove this driver
  drivers: net: 3com: 3c574: Remove this driver
  drivers: net: 3com: 3c515: Remove this driver
  drivers: net: 3com: 3c509: Remove this driver
  net: packetengines: remove obsolete yellowfin driver and vendor dir
  net: packetengines: remove obsolete hamachi driver
  net: remove unused ATM protocols and legacy ATM device drivers
  net: remove ax25 and amateur radio (hamradio) subsystem
  net: remove ISDN subsystem and Bluetooth CMTP
  caif: remove CAIF NETWORK LAYER

net: remove unused ATM protocols and legacy ATM device drivers

2026-04-23T19:21:14+00:00

Remove the ATM protocol modules and PCI/SBUS ATM device drivers
that are no longer in active use.

The ATM core protocol stack, PPPoATM, BR2684, and USB DSL modem
drivers (drivers/usb/atm/) are retained in-tree to maintain PPP
over ATM (PPPoA) and PPPoE-over-BR2684 support for DSL connections.
The Solos ADSL2+ PCI driver is also retained.

Removed ATM protocol modules:
 - net/atm/clip.c - Classical IP over ATM (RFC 2225)
 - net/atm/lec.c - LAN Emulation Client (LANE)
 - net/atm/mpc.c, mpoa_caches.c, mpoa_proc.c - Multi-Protocol Over ATM

Removed PCI/SBUS ATM device drivers (drivers/atm/):
 - adummy, atmtcp - software/testing ATM devices
 - eni - Efficient Networks ENI155P (OC-3, ~1995)
 - fore200e - FORE Systems 200E PCI/SBUS (OC-3, ~1999)
 - he - ForeRunner HE (OC-3/OC-12, ~2000)
 - idt77105 - IDT 77105 25 Mbps ATM PHY
 - idt77252 - IDT 77252 NICStAR II (OC-3, ~2000)
 - iphase - Interphase ATM PCI (OC-3/DS3/E3)
 - lanai - Efficient Networks Speedstream 3010
 - nicstar - IDT 77201 NICStAR (155/25 Mbps, ~1999)
 - suni - PMC S/UNI SONET PHY library

Also clean up references in:
 - net/bridge/ - remove ATM LANE hook (br_fdb_test_addr_hook,
   br_fdb_test_addr)
 - net/core/dev.c - remove br_fdb_test_addr_hook export
 - defconfig files - remove ATM driver config options

The removed code is moved to an out-of-tree module package (mod-orphan).

Acked-by: Andy Shevchenko 
Reviewed-by: Simon Horman 
Reviewed-by: Nikolay Aleksandrov 
Link: https://patch.msgid.link/20260422041846.2035118-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski

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

2026-04-16T10:47:41+00:00

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

net: bridge: add stp_mode attribute for STP mode selection

2026-04-10T22:52:24+00:00

The bridge-stp usermode helper is currently restricted to the initial
network namespace, preventing userspace STP daemons (e.g. mstpd) from
operating on bridges in other network namespaces. Since commit
ff62198553e4 ("bridge: Only call /sbin/bridge-stp for the initial
network namespace"), bridges in non-init namespaces silently fall
back to kernel STP with no way to use userspace STP.

Add a new bridge attribute IFLA_BR_STP_MODE that allows explicit
per-bridge control over STP mode selection:

  BR_STP_MODE_AUTO (default) - Existing behavior: invoke the
    /sbin/bridge-stp helper in init_net only; fall back to kernel STP
    if it fails or in non-init namespaces.

  BR_STP_MODE_USER - Directly enable userspace STP (BR_USER_STP)
    without invoking the helper. Works in any network namespace.
    Userspace is responsible for ensuring an STP daemon manages the
    bridge.

  BR_STP_MODE_KERNEL - Directly enable kernel STP (BR_KERNEL_STP)
    without invoking the helper.

The mode can only be changed while STP is disabled, or set to the
same value (-EBUSY otherwise). IFLA_BR_STP_MODE is processed before
IFLA_BR_STP_STATE in br_changelink(), so both can be set atomically
in a single netlink message. The mode can also be changed in the
same message that disables STP.

The stp_mode struct field is u8 since all possible values fit, while
NLA_U32 is used for the netlink attribute since it occupies the same
space in the netlink message as NLA_U8.

A new stp_helper_active boolean tracks whether the /sbin/bridge-stp
helper was invoked during br_stp_start(), so that br_stp_stop() only
calls the helper for stop when it was called for start. This avoids
calling the helper asymmetrically when stp_mode changes between
start and stop.

Suggested-by: Ido Schimmel 
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Ido Schimmel 
Acked-by: Nikolay Aleksandrov 
Signed-off-by: Andy Roulin 
Link: https://patch.msgid.link/20260405205224.3163000-2-aroulin@nvidia.com
Signed-off-by: Jakub Kicinski