linux-kernel - [PATCH 4.4 14/18] netfilter: ip6_tables: zero-initialize fragment offset

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Date:   Thu, 14 Oct 2021 16:53:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jeremy Sowden <jeremy@...zel.net>,
        Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 14/18] netfilter: ip6_tables: zero-initialize fragment offset

From: Jeremy Sowden <jeremy@...zel.net>

[ Upstream commit 310e2d43c3ad429c1fba4b175806cf1f55ed73a6 ]

ip6tables only sets the `IP6T_F_PROTO` flag on a rule if a protocol is
specified (`-p tcp`, for example).  However, if the flag is not set,
`ip6_packet_match` doesn't call `ipv6_find_hdr` for the skb, in which
case the fragment offset is left uninitialized and a garbage value is
passed to each matcher.

Signed-off-by: Jeremy Sowden <jeremy@...zel.net>
Reviewed-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/ipv6/netfilter/ip6_tables.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 3057356cfdff..43d26625b80f 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -339,6 +339,7 @@ ip6t_do_table(struct sk_buff *skb,
 	 * things we don't know, ie. tcp syn flag or ports).  If the
 	 * rule is also a fragment-specific rule, non-fragments won't
 	 * match it. */
+	acpar.fragoff = 0;
 	acpar.hotdrop = false;
 	acpar.net     = state->net;
 	acpar.in      = state->in;
-- 
2.33.0