From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792706644; b=EqAwx3n5Az4s5ZdEiICXnw+ImscWdzdH/dIz95bFsrV0NbkHlkOgmTfMnhGoudDPuVbv 1mLpTOurQE0lVtYz3sscvPmkvcuXMFCJDPyQEdX8vOG9foiHyJbHwYeswK+BEfh0Qg+03 V/elEdWVgz1b+XggMKg5if+0om3azO8rjP+wqe36X2dAQRAz+6xl9XEZ0+DUQrvKAAFkZ 6o17N7gqHyryZxKra2h0Y5o0s5LrWdvh2Q2xoSrxsiPOv7aMiQBH5deGzoSPwKpfFmCuk 0UhhDNdKn6IicDLpePIWshbWiWImXXOZESnIhbwkSsHsQXs4ZP/S+gC4Qj0rQXgWoGg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792706644; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=BGSGjw3AfRJKhSQYDygDyishNCZub3fivg1QMA60f8g=; b=YxSF27Tb6ZmjS/sgr86Va58cm4F/aZgHqvTWGEn6FMmN7suwk8NAB751ClLDj5Vy7ZDm gagyOOLpCj4EqhWf/btMk4/BlcuihXSixsfOZYXNKzwZKGNhTp1EiBXedEzZVUVjTG9MJ lXapj4AzqDxrIhnmuKC0DY/tvpUrwaibomyQWjyiWqsu3NdE4Qoi2utah0LSBzc3is9aZ mI1QKcv1qzJ5h/6+Nd+cyUoKUA4qghe0SGZNYRjDUKpucJlfLRlLujTgG21lk72uuld16 1VAby/wG7HFo4z5ekbn5+WhjV3ofcgyAMmMAc3zfPCUDr8BrTfVedXu+VPpVmJGG37g== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="FrwT9JO/"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3450D606A319 for ; Thu, 22 Oct 2026 22:04:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=FrwT9JO/ Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD53D1F01825; Thu, 22 Oct 2026 22:04:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792706643; bh=BGSGjw3AfRJKhSQYDygDyishNCZub3fivg1QMA60f8g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FrwT9JO/Hcvy85wiZb4u3hEMQOeuQW5tJxM93b0sUISxLeYYsgNJXlJjxu/Jh/5ZZ 9Un9MTj2FqeLhwtDfPi7VO4oupIZp5sm5ptM37eb+/T6IDkYHJeZsE4VGZLpcYQ43I Bj98KqfnTOjyefIZUhJ+qpLkk+M/IZQ6jbmSY4HN4tMcke6b73lvnSl87vkwFNIgBr owTc0T2fNOQm+u68mXOPV4spn3txYOnf6rSDPBj8vEvQunHkfApb+7Mqq928NA0z7K F6CgX6cCkJ+HSrZjR51afFCXeNSMtJlEG+JnlHMFJdrUHYAY1VCp44JEtP1bF74Urg 4owOIFC7ZSeaw== From: Sasha Levin To: stable@vger.kernel.org Cc: Jun Yang , Nikolay Aleksandrov , TencentOS Corvus AI , Jun Yang , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.10.y] net: bridge: mcast: don't truncate the port group walk on teardown Date: Thu, 22 Oct 2026 18:04:00 -0400 Message-ID: <20261022220239.1982727-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026102217-reuse-backlit-3e7d@gregkh> References: <2026102217-reuse-backlit-3e7d@gregkh> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jun Yang [ Upstream commit 5a3f7a683aee56e1f15c9d53041f3236767eaae7 ] __br_multicast_disable_port_ctx() and br_multicast_del_port() walk port->mglist with hlist_for_each_entry_safe(). However, br_multicast_find_del_pg() can also delete other entries from the same list through br_multicast_fwd_src_remove() or __fwd_del_star_excl(). If such an entry is the iterator's saved next node, hlist_del_init() clears its ->next and terminates the walk early. The reproducer triggers this in both teardown walks, leaving port groups in the bridge mdb with a dangling ->key.port after del_nbp() frees the port: BUG: KASAN: slab-use-after-free in __mdb_fill_info+0x1191/0x1320 __mdb_fill_info+0x1191/0x1320 br_mdb_dump+0x594/0xe40 rtnl_mdb_dump+0x1cf/0x5d0 Use hlist_del_init_rcu() to unlink the group while preserving ->next. br_multicast_del_pg() and the teardown walks run under br->multicast_lock. The GC worker must acquire the same lock before detaching the group for destruction, so the node remains alive while the walk uses the preserved pointer. Preserving ->next means a walk can now reach a group that an earlier iteration already deleted as a side effect. That group is off mp->ports, so br_multicast_find_del_pg() would fall through its port scan and hit the trailing WARN_ON(1). Skip such groups at the top of that helper: a port group is put on port->mglist when it is created and only unlinked when it is deleted, so hlist_unhashed() identifies exactly this case. Fixes: b08123684bd5 ("net: bridge: mcast: install S,G entries automatically based on reports") Cc: stable@vger.kernel.org Suggested-by: Nikolay Aleksandrov Reported-by: TencentOS Corvus AI Signed-off-by: Jun Yang Reviewed-by: Nikolay Aleksandrov Link: https://patch.msgid.link/20260831111330.199543-1-junvyyang@tencent.com Signed-off-by: Jakub Kicinski [ sashal: Applied the br_multicast_del_pg() change to the existing __br_multicast_del_pg() helper. ] Signed-off-by: Sasha Levin --- net/bridge/br_multicast.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index 53dd2d56c37ef..fdaf2db7173e6 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -596,7 +596,11 @@ static void __br_multicast_del_pg(struct net_bridge_mdb_entry *mp, struct hlist_node *tmp; rcu_assign_pointer(*pp, pg->next); - hlist_del_init(&pg->mglist); + /* Keep ->next (held under multicast_lock, freed later by the GC work): + * a port->mglist teardown walk may have latched this node as its next, + * and deleting other groups of the same port must not truncate it. + */ + hlist_del_init_rcu(&pg->mglist); hlist_for_each_entry_safe(ent, tmp, &pg->src_list, node) br_multicast_del_group_src(ent); br_mdb_notify(br->dev, mp, pg, RTM_DELMDB); @@ -629,6 +633,13 @@ static void br_multicast_find_del_pg(struct net_bridge *br, struct net_bridge_mdb_entry *mp; struct net_bridge_port_group *p; + /* A teardown walk over port->mglist can reach a group that an earlier + * iteration already deleted as a side effect. It is off mp->ports by + * now, so skip it instead of falling through to the WARN_ON() below. + */ + if (hlist_unhashed(&pg->mglist)) + return; + mp = br_mdb_ip_get(br, &pg->key.addr); if (WARN_ON(!mp)) return; -- 2.53.0