linux/net/bridge
Lorenzo Bianconi b2870fc216 netfilter: br_netfilter: Reallocate headroom if necessary in neigh_hh_bridge()
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: e179e6322a ("netfilter: bridge-netfilter: Fix MAC header handling with IP DNAT")
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2026-05-16 13:22:50 +02:00
..
netfilter netfilter: bridge: eb_tables: close module init race 2026-05-08 01:30:17 +02:00
br_arp_nd_proxy.c net: bridge: use a stable FDB dst snapshot in RCU readers 2026-04-16 12:47:41 +02:00
br_cfm_netlink.c bridge: cfm: fix enum typo in br_cc_ccm_tx_parse 2023-12-26 22:38:13 +00:00
br_cfm.c bridge: cfm: Fix race condition in peer_mep deletion 2026-03-12 18:33:52 -07:00
br_device.c net: bridge: add stp_mode attribute for STP mode selection 2026-04-10 15:52:24 -07:00
br_fdb.c Delete some obsolete networking code 2026-04-24 09:41:58 -07:00
br_forward.c net: bridge: fix use-after-free due to MST port state bypass 2025-11-06 07:32:17 -08:00
br_if.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
br_input.c net: bridge: fix nd_tbl NULL dereference when IPv6 is disabled 2026-03-05 07:52:56 -08:00
br_ioctl.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
br_mdb.c Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses 2026-02-22 08:26:33 -08:00
br_mrp_netlink.c bridge: mrp: reject zero test interval to avoid OOM panic 2026-03-31 16:11:24 +02:00
br_mrp_switchdev.c bridge: mrp: Extend br_mrp_switchdev to detect better the errors 2021-02-16 14:47:46 -08:00
br_mrp.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
br_mst.c net: bridge: fix MST static key usage 2025-11-06 07:32:17 -08:00
br_multicast_eht.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
br_multicast.c treewide: Replace kmalloc with kmalloc_obj for non-scalar types 2026-02-21 01:02:28 -08:00
br_netfilter_hooks.c netfilter: br_netfilter: Reallocate headroom if necessary in neigh_hh_bridge() 2026-05-16 13:22:50 +02:00
br_netfilter_ipv6.c netfilter: remove nf_ipv6_ops and use direct function calls 2026-03-29 11:21:24 -07:00
br_netlink_tunnel.c net: bridge: fix an inconsistent indentation 2024-06-05 10:04:47 +01:00
br_netlink.c net: bridge: add stp_mode attribute for STP mode selection 2026-04-10 15:52:24 -07:00
br_nf_core.c bridge: netfilter: Fix forwarding of fragmented packets 2025-05-16 16:02:06 -07:00
br_private_cfm.h bridge: cfm: Kernel space implementation of CFM. CCM frame RX added. 2020-10-29 18:39:43 -07:00
br_private_mcast_eht.h net: bridge: multicast: use multicast contexts instead of bridge or port 2021-07-20 05:41:19 -07:00
br_private_mrp.h net: bridge: mrp: Update the Test frames for MRA 2021-06-28 15:46:10 -07:00
br_private_stp.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
br_private_tunnel.h bridge: always declare tunnel functions 2023-05-17 21:28:58 -07:00
br_private.h net: remove unused ATM protocols and legacy ATM device drivers 2026-04-23 12:21:14 -07:00
br_stp_bpdu.c move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
br_stp_if.c net: bridge: add stp_mode attribute for STP mode selection 2026-04-10 15:52:24 -07:00
br_stp_timer.c treewide, timers: Rename from_timer() to timer_container_of() 2025-06-08 09:07:37 +02:00
br_stp.c treewide: Switch/rename to timer_delete[_sync]() 2025-04-05 10:30:12 +02:00
br_switchdev.c bridge: No DEV_PATH_BR_VLAN_UNTAG_HW for dsa foreign 2026-03-19 13:14:00 +01:00
br_sysfs_br.c mm.git review status for linus..mm-nonmm-stable 2026-02-12 12:13:01 -08:00
br_sysfs_if.c net: bridge: use sysfs_emit instead of sprintf 2026-02-03 19:19:42 -08:00
br_vlan_options.c bridge: Check relevant per-VLAN options in VLAN range grouping 2026-02-26 19:24:29 -08:00
br_vlan_tunnel.c bridge: fix C-VLAN preservation in 802.1ad vlan_tunnel egress 2026-01-04 09:45:35 -08:00
br_vlan.c bridge: No DEV_PATH_BR_VLAN_UNTAG_HW for dsa foreign 2026-03-19 13:14:00 +01:00
br.c net: remove unused ATM protocols and legacy ATM device drivers 2026-04-23 12:21:14 -07:00
Kconfig ipv6: convert CONFIG_IPV6 to built-in only and clean up Kconfigs 2026-03-29 11:21:22 -07:00
Makefile net: bridge: mst: Multiple Spanning Tree (MST) mode 2022-03-17 16:49:57 -07:00