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

[Xin Long]

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....@gmail.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