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 <[email protected]>
---
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 <[email protected]>
