netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm

Wang Liang · Florian Westphal · commit 479a54ab9208 · 2025-08-27T11:53:37.000+02:00
When send a broadcast packet to a tap device, which was added to a bridge, br_nf_local_in() is called to confirm the conntrack. If another conntrack with the same hash value is added to the hash table, which can be triggered by a normal packet to a non-bridge device, the below warning may happen. ------------[ cut here ]------------ WARNING: CPU: 1 PID: 96 at net/bridge/br_netfilter_hooks.c:632 br_nf_local_in+0x168/0x200 CPU: 1 UID: 0 PID: 96 Comm: tap_send Not tainted 6.17.0-rc2-dirty #44 PREEMPT(voluntary) RIP: 0010:br_nf_local_in+0x168/0x200 Call Trace: <TASK> nf_hook_slow+0x3e/0xf0 br_pass_frame_up+0x103/0x180 br_handle_frame_finish+0x2de/0x5b0 br_nf_hook_thresh+0xc0/0x120 br_nf_pre_routing_finish+0x168/0x3a0 br_nf_pre_routing+0x237/0x5e0 br_handle_frame+0x1ec/0x3c0 __netif_receive_skb_core+0x225/0x1210 __netif_receive_skb_one_core+0x37/0xa0 netif_receive_skb+0x36/0x160 tun_get_user+0xa54/0x10c0 tun_chr_write_iter+0x65/0xb0 vfs_write+0x305/0x410 ksys_write+0x60/0xd0 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK> ---[ end trace 0000000000000000 ]--- To solve the hash conflict, nf_ct_resolve_clash() try to merge the conntracks, and update skb->_nfct. However, br_nf_local_in() still use the old ct from local variable 'nfct' after confirm(), which leads to this warning. If confirm() does not insert the conntrack entry and return NF_DROP, the warning may also occur. There is no need to reserve the WARN_ON_ONCE, just remove it. Link: https://lore.kernel.org/netdev/20250820043329.2902014-1-wangliang74@huawei.com/ Fixes: 62e7151 ("netfilter: bridge: confirm multicast packets before passing them up the stack") Suggested-by: Florian Westphal <fw@strlen.de> Signed-off-by: Wang Liang <wangliang74@huawei.com> Signed-off-by: Florian Westphal <fw@strlen.de>
diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
@@ -626,9 +626,6 @@ static unsigned int br_nf_local_in(void *priv,
 		break;
 	}
 
-	ct = container_of(nfct, struct nf_conn, ct_general);
-	WARN_ON_ONCE(!nf_ct_is_confirmed(ct));
-
 	return ret;
 }
 #endif

Original file line number	Diff line number	Diff line change
`@@ -626,9 +626,6 @@ static unsigned int br_nf_local_in(void *priv,`
`626`	`626`	`break;`
`627`	`627`	`}`
`628`	`628`
`629`		`- ct = container_of(nfct, struct nf_conn, ct_general);`
`630`		`- WARN_ON_ONCE(!nf_ct_is_confirmed(ct));`
`631`		`-`
`632`	`629`	`return ret;`
`633`	`630`	`}`
`634`	`631`	`#endif`