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 78FBD42FCC9; Tue, 21 Jul 2026 19:41:41 +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=1784662902; cv=none; b=ES6F+EJExzD3Msqo2q8zUP52C1Tuo1PVRDI/YHlIDo2Yagllha+zpFy2PYfz+4q8PtQCi1mdHzcjmq+eGEfzXaSGbnMSKW3bfi0iwq0S4hrL973HZpIp+F5ePhmCmjtsuqd4xPXQ+3zAhVJ9cbAnV3PcNU+SD3aUtFEe3FJD9cw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784662902; c=relaxed/simple; bh=uMWU1uTaroGcSrSL8j+y9Mw5QQv0H+Hmv7IxjT6n7aw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=PwAxEniIYAMiQsPqCbAT0YO+hs5zlg/Di5Besn1RSLlVbXTODvPK2BBdrm7Q7WiTQxiZGeBmzp3LqnD/IaBzRyaEjG35K0Wi1fxG7904SFObp4a6buuvVQODyBzKCSqQxasQ/3/3ScGsOZzYt8NCiXfJqhbAU3yIFvhC+KTwic0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UlntoQvn; 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="UlntoQvn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DDB551F000E9; Tue, 21 Jul 2026 19:41:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784662901; bh=mV7H1OBgEqtRePmkMwBzl6fc1VnBaoRR48jUbN47lD4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UlntoQvnX/nODTLf6RgvekmcjbRlpgtBI7kSordxD5Nda3YRZathpXAS3lOeCjzIJ UReOWytI5YYHC0C74hYYmiJrwCAWjYBRaQPJt9ILgyDb2JEwLlAU+fmIJo+x/XSYi5 Cuyqg7jZ0hZDKo/XnVdjIUO0/9zc4sHv0KGP5AC4= 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 6.12 0620/1276] bpf: zero-initialize the fib lookup flow struct Date: Tue, 21 Jul 2026 17:17:43 +0200 Message-ID: <20260721152459.982401062@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152446.065700225@linuxfoundation.org> References: <20260721152446.065700225@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 6.12-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 80aa924d3e649d..6450aa2ea44efc 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6007,7 +6007,7 @@ 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; @@ -6147,7 +6147,7 @@ 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