From c47ca77fee9071aa543bae592dd2a384f895c8b6 Mon Sep 17 00:00:00 2001 From: Wang Liang Date: Fri, 22 Aug 2025 11:52:19 +0800 Subject: netfilter: br_netfilter: do not check confirmed bit in br_nf_local_in() after confirm [ Upstream commit 479a54ab92087318514c82428a87af2d7af1a576 ] 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: 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 ---[ 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: 62e7151ae3eb ("netfilter: bridge: confirm multicast packets before passing them up the stack") Suggested-by: Florian Westphal Signed-off-by: Wang Liang Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin --- net/bridge/br_netfilter_hooks.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c index 17a5f5923d61..5ad3f3ef4ca7 100644 --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -653,9 +653,6 @@ 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 -- cgit v1.2.3