From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7B143521895; Wed, 30 Sep 2026 17:32:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790789554; cv=none; b=WZu3S7hHlL9/5lqfE16ggRtZe+eZTSm/8lP8FAUlnsRqE+xdnycXUDnCnapmpzLMMgjvpiK+BuJiAWcfJoa/ZoXDr3QJtAtQPLToYzNTMVI8+oSs+hnKGQ6MiCxB4Ed3jXvRWisvM/VTyTaaFqH9QOWcLmLn9ILJQPiOPQu/7AM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790789554; c=relaxed/simple; bh=AMK9SK/r8vTeIWbRXijnXMftJKhHqDxJmn3zWiPxJjE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kAwTZlvCWD6aCXqW3TWxQs7wbJ/1djO1s/ofbvtcKjZvbXvLlR0mr9qiUiUSaiELvonv4InrZj6C0a43w4SBS5+5znFgywSUIb2M1XMasTlBx/kEPU+y0Bkm/4somwmlHjNjRv2+ShgGVkcqKCE55jehnGEjpqZG+Ugc6WirmR4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=GqTZ5Gmr; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="GqTZ5Gmr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CCA8C1F000FF; Wed, 30 Sep 2026 17:32:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790789553; bh=XUqxKcrA+Qk5OvZ+VAIPW2y+pS4oTKm1XA0JOvDTkWA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=GqTZ5GmrBhdaaFX6pGWzG2lOg+virB8hVvXhApk8c0jDdWMvA0JHhEm3khoYp7apz NJUBxQtSujx/ozFKZ0lV1lwW6JK2J2DKMxw4jABNK9xY4Mo12MdP+V4i2Ddik5NuJg L5pdIaqj9AmtOj9eUHPl8SFpFeup3L+cMnJI3jWg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, co+459f67f4d8af8ce6@bugs.sh, Florian Westphal , Weiming Shi , Pablo Neira Ayuso Subject: [PATCH 6.12 518/877] netfilter: ip6t_rpfilter: reject routes without inet6_dev Date: Wed, 30 Sep 2026 17:23:49 +0200 Message-ID: <20260930152425.830997844@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152414.738996857@linuxfoundation.org> References: <20260930152414.738996857@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Weiming Shi commit 1b9b5323725e458906c7620a3bc10398b51ad954 upstream. ip6_route_lookup() can return an error-free route whose rt6i_idev is NULL. Lowering an external nexthop device's MTU below IPV6_MIN_MTU tears down its inet6_dev while fib6_ifdown() leaves routes using nexthop objects in the FIB. An unprivileged user can construct this state with rtnetlink in a private user and network namespace, then trigger a NULL dereference through an IPv6 rpfilter lookup: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: rpfilter_mt (net/ipv6/netfilter/ip6t_rpfilter.c:75) Call Trace: ip6t_do_table (net/ipv6/netfilter/ip6_tables.c:316) nf_hook_slow (net/netfilter/core.c:619) ipv6_rcv (net/ipv6/ip6_input.c:351) __netif_receive_skb_one_core (net/core/dev.c:6216) process_backlog (net/core/dev.c:6680) __napi_poll (net/core/dev.c:7739) net_rx_action (net/core/dev.c:7959) handle_softirqs (kernel/softirq.c:622) do_softirq.part.0 (kernel/softirq.c:523) __local_bh_enable_ip (kernel/softirq.c:450) __dev_queue_xmit (net/core/dev.c:4913) packet_sendmsg (net/packet/af_packet.c:3139) __sys_sendto (net/socket.c:2252) __x64_sys_sendto (net/socket.c:2259) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Kernel panic - not syncing: Fatal exception in interrupt Reject routes without an inet6_dev immediately after lookup. Such routes are not eligible for reverse-path filtering, and the check protects all later rt6i_idev dereferences. Fixes: e26f9a480fb6 ("netfilter: add ipv6 reverse path filter match") Reported-by: co+459f67f4d8af8ce6@bugs.sh Closes: https://lore.kernel.org/all/VtWUkE8QzJt5CroTj2V2v3ZQ0gwbXZ7nq7I3@bugs.sh/ Suggested-by: Florian Westphal Assisted-by: Claude:gpt-5 Cc: stable@vger.kernel.org Signed-off-by: Weiming Shi Signed-off-by: Pablo Neira Ayuso Signed-off-by: Greg Kroah-Hartman --- net/ipv6/netfilter/ip6t_rpfilter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/ipv6/netfilter/ip6t_rpfilter.c +++ b/net/ipv6/netfilter/ip6t_rpfilter.c @@ -61,7 +61,7 @@ static bool rpfilter_lookup_reverse6(str fl6.flowi6_oif = dev->ifindex; rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags); - if (rt->dst.error) + if (rt->dst.error || !rt->rt6i_idev) goto out; if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))