From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 391C933D506; Fri, 8 May 2026 11:25:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778239540; cv=none; b=EaqlWxqT8OY1PQQGFqmwTYube0wlRuuiyBC+Ywf9BFtnX3uV5TucV+JTNk5IeCX26wEtoto068edub8gavJXocxH+shzmiuMIVfyxemtgqiLW/uhcbT33gMq1HjHaMgY9YgsD+LSpeDYzR2oaxIauCI8Kz02ME/Zt/LazwDJvMM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778239540; c=relaxed/simple; bh=tz0eZGnrl6wId4LnLK2yrH+5fHe4AC68YMgQAi103mY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=iKeHKifTs8vRRbeaVCK8WTn7BFJQ+dOTJ89QOeGxuoREHIa8S0cvXaoUt1xRDELTIW/mdb7QGNAIcjWjFz2wIanFQOQiBcsc4d2xosGHbVm5RpVWwAS9b2IByCNnATThTYEjv9xFWQfjAEZbJLldymGGscF3zVu/ksaMOWqBTt0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JLg/6xzM; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JLg/6xzM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60A55C2BCB0; Fri, 8 May 2026 11:25:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778239539; bh=tz0eZGnrl6wId4LnLK2yrH+5fHe4AC68YMgQAi103mY=; h=From:Date:Subject:To:Cc:From; b=JLg/6xzM6NrEJIPS0+Z/e8yP4ikju6KV6x6ilghcOTY+3fBi4n+tYG4BSF0IkVl9j gUDfq6mAAGC+olZqNBtfuOBQGu0QLMMQo96hA2/1ZER+oXitT51tugIKjp4fROMvMg 1UQn3FIjSOYxvQAaEH1ktnIkeNHNzBW2+7cdJn482wKX2IIrqqsblrzSUN0cVLgrL5 rMLbzIfrf5CJBYLNq8rmqeHuAsmqGSm7KjZR4USJAI65f/aFY/LZ1TTrArp5iCSd2W kkJoNgxs/q8HtUszoOa2zKHd0Sn3qy3b9bicTtZI877UptYIShCvXEqjCnrcm1vQ/2 oEovWOPuEKDog== From: Lorenzo Bianconi Date: Fri, 08 May 2026 13:25:14 +0200 Subject: [PATCH net] net: neigh: Reallocate headroom if necessary in neigh_hh_bridge() Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260508-nf-neigh_hh_bridge-fix-v1-1-a1464468d92e@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/x2MSQqAMBAEvyJzNhAjrl8REZfWzGWUREQQ/+7gs ZrqeigiMCK1yUMBF0feRSFLE5r9KBsML8rkrCttYWsjqxHw5gfvhynwosbKt2nGqaoKwOVzSXo +AnT+wx0JTurf9wNVYzFKbQAAAA== X-Change-ID: 20260508-nf-neigh_hh_bridge-fix-9ab775ee23c6 To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Pablo Neira Ayuso , Florian Westphal , Phil Sutter , Nikolay Aleksandrov , Ido Schimmel , Bart De Schuymer , Patrick McHardy Cc: netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, bridge@lists.linux.dev, Lorenzo Bianconi X-Mailer: b4 0.14.3 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") Signed-off-by: Lorenzo Bianconi --- include/net/neighbour.h | 15 +++++++++++---- net/bridge/br_netfilter_hooks.c | 5 ++++- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/include/net/neighbour.h b/include/net/neighbour.h index 2dfee6d4258a..4e1222968753 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -487,16 +487,23 @@ 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) +static inline struct sk_buff * +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); + + if (unlikely(skb_headroom(skb) < hh_alen)) { + skb = skb_expand_head(skb, hh_alen); + if (!skb) + return NULL; + } 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; + + return skb; } #endif diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c index 0ab1c94db4b9..6b59d7eb7906 100644 --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -297,7 +297,10 @@ int br_nf_pre_routing_finish_bridge(struct net *net, struct sock *sk, struct sk_ goto free_skb; } - neigh_hh_bridge(&neigh->hh, skb); + skb = neigh_hh_bridge(&neigh->hh, skb); + if (!skb) + return -ENOMEM; + skb->dev = br_indev; ret = br_handle_frame_finish(net, sk, skb); --- base-commit: fcee7d82f27d6a8b1ddc5bbefda59b4e441e9bc0 change-id: 20260508-nf-neigh_hh_bridge-fix-9ab775ee23c6 Best regards, -- Lorenzo Bianconi