[PATCH 4.14 098/146] sctp: make sure stream nums can match optlen in sctp_setsockopt_reset_streams

Greg Kroah-Hartman
2018-01-01T14:44:47Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 2342b8d95bcae5946e1b9b8d58645f37500ef2e7 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/socket.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3874,13 +3874,17 @@ static int sctp_setsockopt_reset_streams
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;