netdev - [PATCH nf] netfilter/xt_sctp: validate the flag

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Date: Mon, 28 Aug 2023 19:12:55 -0300
From: Wander Lairson Costa <wander@...hat.com>
To: Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	Florian Westphal <fw@...len.de>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Harald Welte <laforge@...filter.org>,
	netfilter-devel@...r.kernel.org (open list:NETFILTER),
	coreteam@...filter.org (open list:NETFILTER),
	netdev@...r.kernel.org (open list:NETWORKING [GENERAL]),
	linux-kernel@...r.kernel.org (open list)
Cc: Wander Lairson Costa <wander@...hat.com>,
	Lucas Leong <wmliang@...osec.exchange>,
	stable@...nel.org
Subject: [PATCH nf] netfilter/xt_sctp: validate the flag_info count

sctp_mt_check doesn't validate the flag_count field. An attacker can
take advantage of that to trigger a OOB read and leak memory
information.

Add the field validation in the checkentry function.

Fixes: 2e4e6a17af35 ("[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables")
Reported-by: Lucas Leong <wmliang@...osec.exchange>
Cc: stable@...nel.org
Signed-off-by: Wander Lairson Costa <wander@...hat.com>
---
 net/netfilter/xt_sctp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/xt_sctp.c b/net/netfilter/xt_sctp.c
index e8961094a282..b46a6a512058 100644
--- a/net/netfilter/xt_sctp.c
+++ b/net/netfilter/xt_sctp.c
@@ -149,6 +149,8 @@ static int sctp_mt_check(const struct xt_mtchk_param *par)
 {
 	const struct xt_sctp_info *info = par->matchinfo;
 
+	if (info->flag_count > ARRAY_SIZE(info->flag_info))
+		return -EINVAL;
 	if (info->flags & ~XT_SCTP_VALID_FLAGS)
 		return -EINVAL;
 	if (info->invflags & ~XT_SCTP_VALID_FLAGS)
-- 
2.41.0