From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: Mon, 8 Jan 2018 19:02:28 -0200
Subject: sctp: add a ceiling to optlen in some sockopts
Git-commit: 5960cefab9df76600a1a7d4ff592c59e14616e88
Patch-mainline: v4.15-rc8
References: bnc#1129163

Hangbin Liu reported that some sockopt calls could cause the kernel to log
a warning on memory allocation failure if the user supplied a large optlen
value. That is because some of them called memdup_user() without a ceiling
on optlen, allowing it to try to allocate really large buffers.

This patch adds a ceiling by limiting optlen to the maximum allowed that
would still make sense for these sockopt.

Reported-by: Hangbin Liu <haliu@redhat.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 net/sctp/socket.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3472,6 +3472,8 @@ static int sctp_setsockopt_hmac_ident(st
 
 	if (optlen < sizeof(struct sctp_hmacalgo))
 		return -EINVAL;
+	optlen = min_t(unsigned int, optlen, sizeof(struct sctp_hmacalgo) +
+					     SCTP_AUTH_NUM_HMACS * sizeof(u16));
 
 	hmacs = memdup_user(optval, optlen);
 	if (IS_ERR(hmacs))
@@ -3510,6 +3512,11 @@ static int sctp_setsockopt_auth_key(stru
 
 	if (optlen <= sizeof(struct sctp_authkey))
 		return -EINVAL;
+	/* authkey->sca_keylength is u16, so optlen can't be bigger than
+	 * this.
+	 */
+	optlen = min_t(unsigned int, optlen, USHRT_MAX +
+					     sizeof(struct sctp_authkey));
 
 	authkey = memdup_user(optval, optlen);
 	if (IS_ERR(authkey))
@@ -3867,6 +3874,9 @@ static int sctp_setsockopt_reset_streams
 
 	if (optlen < sizeof(*params))
 		return -EINVAL;
+	/* srs_number_streams is u16, so optlen can't be bigger than this. */
+	optlen = min_t(unsigned int, optlen, USHRT_MAX +
+					     sizeof(__u16) * sizeof(*params));
 
 	params = memdup_user(optval, optlen);
 	if (IS_ERR(params))