[PATCH 4.12 058/106] sctp: fix an array overflow when all ext chunks are set

[Greg Kroah-Hartman]

4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xin Long <lucien.xin@xxxxxxxxx>


[ Upstream commit 10b3bf54406bb7f4e78da9bb2a485c5c986678ad ]

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@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sctp/sm_make_chunk.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 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
 	sctp_adaptation_ind_param_t aiparam;
 	sctp_supported_ext_param_t ext_param;
 	int num_ext = 0;
-	__u8 extensions[3];
+	__u8 extensions[4];
 	sctp_paramhdr_t *auth_chunks = NULL,
 			*auth_hmacs = NULL;
 
@@ -396,7 +396,7 @@ struct sctp_chunk *sctp_make_init_ack(co
 	sctp_adaptation_ind_param_t aiparam;
 	sctp_supported_ext_param_t ext_param;
 	int num_ext = 0;
-	__u8 extensions[3];
+	__u8 extensions[4];
 	sctp_paramhdr_t *auth_chunks = NULL,
 			*auth_hmacs = NULL,
 			*auth_random = NULL;