From: Pablo Neira Ayuso <pablo@netfilter.org>
To: netfilter-devel@vger.kernel.org
Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org,
pabeni@redhat.com, edumazet@google.com, fw@strlen.de,
horms@kernel.org
Subject: [PATCH net 11/12] netfilter: br_netfilter: Reallocate headroom if necessary in neigh_hh_bridge()
Date: Sat, 16 May 2026 13:56:26 +0200 [thread overview]
Message-ID: <20260516115627.967773-12-pablo@netfilter.org> (raw)
In-Reply-To: <20260516115627.967773-1-pablo@netfilter.org>
From: Lorenzo Bianconi <lorenzo@kernel.org>
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 <idosch@nvidia.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
include/net/neighbour.h | 8 ++++++--
net/bridge/br_netfilter_hooks.c | 6 +++++-
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 2dfee6d4258a..8860cc2175fc 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -489,11 +489,15 @@ static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
static inline int neigh_hh_bridge(struct hh_cache *hh, struct sk_buff *skb)
{
- unsigned int seq, hh_alen;
+ unsigned int seq, hh_alen = HH_DATA_ALIGN(ETH_HLEN);
+ int err;
+
+ err = skb_cow_head(skb, hh_alen);
+ if (err)
+ return err;
do {
seq = read_seqbegin(&hh->hh_lock);
- hh_alen = HH_DATA_ALIGN(ETH_HLEN);
memcpy(skb->data - hh_alen, hh->hh_data, ETH_ALEN + hh_alen - ETH_HLEN);
} while (read_seqretry(&hh->hh_lock, seq));
return 0;
diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
index 0ab1c94db4b9..0a394e5f4391 100644
--- a/net/bridge/br_netfilter_hooks.c
+++ b/net/bridge/br_netfilter_hooks.c
@@ -297,7 +297,11 @@ int br_nf_pre_routing_finish_bridge(struct net *net, struct sock *sk, struct sk_
goto free_skb;
}
- neigh_hh_bridge(&neigh->hh, skb);
+ if (neigh_hh_bridge(&neigh->hh, skb)) {
+ neigh_release(neigh);
+ goto free_skb;
+ }
+
skb->dev = br_indev;
ret = br_handle_frame_finish(net, sk, skb);
--
2.47.3
next prev parent reply other threads:[~2026-05-16 11:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-16 11:56 [PATCH net 00/12] Netfilter/IPVS fixes for net Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 01/12] netfilter: nf_conntrack_helper: fix possible null deref during error log Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 02/12] ipvs: avoid possible loop in ip_vs_dst_event on resizing Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 03/12] netfilter: ipset: fix a potential dump-destroy race Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 04/12] netfilter: nft_inner: Fix IPv6 inner_thoff desync Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 05/12] netfilter: ipset: stop hash:* range iteration at end Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 06/12] netfilter: nft_inner: release local_lock before re-enabling softirqs Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 07/12] netfilter: ip6t_hbh: reject oversized option lists Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 08/12] netfilter: ipset: Fix data race between add and list header in all hash types Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 09/12] netfilter: ipset: Fix data race between add and dump " Pablo Neira Ayuso
2026-05-16 11:56 ` [PATCH net 10/12] netfilter: ipset: annotate "pos" for concurrent readers/writers Pablo Neira Ayuso
2026-05-16 11:56 ` Pablo Neira Ayuso [this message]
2026-05-16 11:56 ` [PATCH net 12/12] netfilter: nf_queue: hold bridge skb->dev while queued Pablo Neira Ayuso
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