netdev - [PATCH net] sctp: fix an array overflow when all ext chunks are set

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Message-Id: <3e78f6040b834ee9221cd2ebf539324499a8bb4f.1500041253.git.lucien.xin@gmail.com>
Date:   Fri, 14 Jul 2017 22:07:33 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org
Cc:     davem@...emloft.net,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>
Subject: [PATCH net] sctp: fix an array overflow when all ext chunks are set

Marcelo noticed an array overflow caused by commit c28445c3cb07
("sctp: add reconf_enable in asoc ep and netns"), in which sctp
would add SCTP_CID_RECONF into extensions when reconf_enable is
set in sctp_make_init and sctp_make_init_ack.

Then now when all ext chunks are set, 4 ext chunk ids can be put
into extensions array while extensions array size is 3. It would
cause a kernel panic because of this overflow.

This patch is to fix it by defining extensions array size is 4 in
both sctp_make_init and sctp_make_init_ack.

Fixes: c28445c3cb07 ("sctp: add reconf_enable in asoc ep and netns")
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/sctp/sm_make_chunk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 4e16b02..6110447 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -228,7 +228,7 @@ struct sctp_chunk *sctp_make_init(const struct sctp_association *asoc,
 	sctp_adaptation_ind_param_t aiparam;
 	sctp_supported_ext_param_t ext_param;
 	int num_ext = 0;
-	__u8 extensions[3];
+	__u8 extensions[4];
 	struct sctp_paramhdr *auth_chunks = NULL,
 			*auth_hmacs = NULL;
 
@@ -396,7 +396,7 @@ struct sctp_chunk *sctp_make_init_ack(const struct sctp_association *asoc,
 	sctp_adaptation_ind_param_t aiparam;
 	sctp_supported_ext_param_t ext_param;
 	int num_ext = 0;
-	__u8 extensions[3];
+	__u8 extensions[4];
 	struct sctp_paramhdr *auth_chunks = NULL,
 			*auth_hmacs = NULL,
 			*auth_random = NULL;
-- 
2.1.0