sctp: make sure stream nums can match optlen in sctp_setsockopt_reset_streams

Now in sctp_setsockopt_reset_streams, it only does the check
optlen < sizeof(*params) for optlen. But it's not enough, as
params->srs_number_streams should also match optlen.

If the streams in params->srs_stream_list are less than stream
nums in params->srs_number_streams, later when dereferencing
the stream list, it could cause a slab-out-of-bounds crash, as
reported by syzbot.

This patch is to fix it by also checking the stream numbers in
sctp_setsockopt_reset_streams to make sure at least it's not
greater than the streams in the list.

Fixes: 7f9d68ac944e ("sctp: implement sender-side procedures for SSN Reset Request Parameter")
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 1 deletions

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index eb17a911aa29..3253f724a995 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3891,13 +3891,17 @@ static int sctp_setsockopt_reset_streams(struct sock *sk,
         struct sctp_association *asoc;
         int retval = -EINVAL;
 
-        if (optlen < sizeof(struct sctp_reset_streams))
+        if (optlen < sizeof(*params))
                 return -EINVAL;
 
         params = memdup_user(optval, optlen);
         if (IS_ERR(params))
                 return PTR_ERR(params);
 
+        if (params->srs_number_streams * sizeof(__u16) >
+            optlen - sizeof(*params))
+                goto out;
+
         asoc = sctp_id2assoc(sk, params->srs_assoc_id);
         if (!asoc)
                 goto out;