netdev - [PATCH net 2/5] netfilter: xt_sctp: validate the flag

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Message-Id: <20230830235935.465690-3-pablo@netfilter.org>
Date: Thu, 31 Aug 2023 01:59:32 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com
Subject: [PATCH net 2/5] netfilter: xt_sctp: validate the flag_info count

From: Wander Lairson Costa <wander@...hat.com>

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")
Cc: stable@...r.kernel.org
Reported-by: Lucas Leong <wmliang@...osec.exchange>
Signed-off-by: Wander Lairson Costa <wander@...hat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 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)
-- 
2.30.2