The 'sched' index value must be checked before accessing an element
of the 'sctp_sched_ops' array. Otherwise, it can lead to buffer overflow.

Note that it's harmless since the 'sched' parameter is checked before
calling 'sctp_sched_set_sched'.

Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with SVACE.

Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
Reviewed-by: Simon Horman <redacted>
Signed-off-by: Ilia.Gavrilov <redacted>
---
V2:
 - Change the order of local variables
 - Specify the target tree in the subject
 net/sctp/stream_sched.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
index 330067002deb..4d076a9b8592 100644
--- a/net/sctp/stream_sched.c
+++ b/net/sctp/stream_sched.c

@@ -146,18 +146,19 @@ static void sctp_sched_free_sched(struct sctp_stream *stream)
 int sctp_sched_set_sched(struct sctp_association *asoc,
                         enum sctp_sched_type sched)
 {
-       struct sctp_sched_ops *n = sctp_sched_ops[sched];
        struct sctp_sched_ops *old = asoc->outqueue.sched;
        struct sctp_datamsg *msg = NULL;
+       struct sctp_sched_ops *n;
        struct sctp_chunk *ch;
        int i, ret = 0;

-       if (old == n)
-               return ret;
-
        if (sched > SCTP_SS_MAX)
                return -EINVAL;

+       n = sctp_sched_ops[sched];
+       if (old == n)
+               return ret;
+
        if (old)
                sctp_sched_free_sched(&asoc->stream);

--

2.30.2