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 1AD343B42CB; Tue, 21 Jul 2026 22:13:20 +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=1784672001; cv=none; b=FHin0r5K9BvNIL0rL5BN/ScRZQOjz7oqm8Jjqc2bzUztlqBB9uftjsgPu8UpR6VA3U80+eYYScKXtVgDaoFbYRiItocxQKmPMIvgGqd2hfiOWPG/3Hje7zvnWrxD47W5VGkOTjON2A/8iLUbCBco8mUjHH1VRCnSPVyIjYjzyt8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784672001; c=relaxed/simple; bh=ZBLiroSfsuU+DTCo52+3+9a0Bf65gYTp0d0T79jeDtI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=lEdQE/IWEm3VKC5RXUXe6ZrAbNB3epR65WHll6twNu9Esl5gX+Wv2VFGDTGK7oN5q+Q6Rxxi/3qoiilqFSAfdtMKQeQlI0oVCEjMQUcfQuzA2jCRdxcQBxosoIbEtzX5jioMqjYknpq5rz+EH2Fwq7vq2jdXZ3Ynvh6j8LWmkqI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UEw6LeD4; 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="UEw6LeD4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A8111F000E9; Tue, 21 Jul 2026 22:13:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784672000; bh=ZszhS6BYykfmpS6OMLQHWM3UBSDTTLii/KCvCaAvaUw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UEw6LeD4w6FonVqxox+a2P3dGYuACLHfTBT2pwMlljgSH9N+U1AGYIHtbgA4t1jxd WKgDZaezQ5qMaZ3RWHT8imy+SJgsqI7tmWVmYZ9MUekaFIMhYuasPM3XG18pSGbzeu +5aitm2rqhkBlOf17asGQPxs3mLk1IQt/HyKo2PY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Avinash Duduskar , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , Alexei Starovoitov , Sasha Levin Subject: [PATCH 5.15 460/843] bpf: zero-initialize the fib lookup flow struct Date: Tue, 21 Jul 2026 17:21:35 +0200 Message-ID: <20260721152416.379427194@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152405.946368001@linuxfoundation.org> References: <20260721152405.946368001@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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Avinash Duduskar [ Upstream commit 0dfcb68a6a5ac517b22dff6a1f01cb4f126dfc57 ] bpf_ipv4_fib_lookup() and bpf_ipv6_fib_lookup() build the flow key on the stack with a bare "struct flowi4 fl4;" / "struct flowi6 fl6;" and fill it field by field, but never set flowi4_l3mdev / flowi6_l3mdev. On the non-DIRECT path the lookup goes through the fib rules whenever the netns has custom rules, which a VRF installs: bpf_ipv4_fib_lookup() -> fib_lookup() -> __fib_lookup() -> l3mdev_update_flow() reads !fl->flowi_l3mdev -> fib_rules_lookup() -> fib_rule_match() -> l3mdev_fib_rule_match() uses fl->flowi_l3mdev l3mdev_update_flow() resolves the l3mdev master from the ingress device only while the field is still zero. Left at a nonzero stack value the resolution is skipped, and l3mdev_fib_rule_match() then tests that value as an ifindex, so the VRF master is not resolved and the rule fails to match: an ingress enslaved to a VRF can fail to select its table. FIB rules matching on an L3 master device (l3mdev_fib_rule_iif_match()/ _oif_match()) read the same value, so an "ip rule iif/oif " mismatches the same way. Zero-initialize the whole flow struct rather than adding one more field assignment, so any flowi field added later is covered too. ip_route_input_slow() likewise zeroes the field before its input lookup. CONFIG_INIT_STACK_ALL_ZERO masks this by default, but it depends on compiler support (CC_HAS_AUTO_VAR_INIT_ZERO), so INIT_STACK_NONE builds, including older toolchains that fall back to it, are exposed. Built with INIT_STACK_ALL_PATTERN, a plain bpf_fib_lookup (no VLAN, no DIRECT) over a VRF slave whose destination is routed only in the VRF table returns BPF_FIB_LKUP_RET_NOT_FWDED, and resolves with this patch. On the default config the lookup succeeds either way, so ordinary testing does not catch the bug. Fixes: 40867d74c374 ("net: Add l3mdev index to flow struct and avoid oif reset for port devices") Signed-off-by: Avinash Duduskar Reviewed-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/r/20260617224719.1428599-1-avinash.duduskar@gmail.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- net/core/filter.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index aee29ec9824425..72807bea81ec53 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5588,7 +5588,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, struct neighbour *neigh; struct net_device *dev; struct fib_result res; - struct flowi4 fl4; + struct flowi4 fl4 = {}; u32 mtu = 0; int err; @@ -5725,7 +5725,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, struct neighbour *neigh; struct net_device *dev; struct inet6_dev *idev; - struct flowi6 fl6; + struct flowi6 fl6 = {}; int strict = 0; int oif, err; u32 mtu = 0; -- 2.53.0