[PATCH AUTOSEL for 4.14 105/110] sctp: add a ceiling to optlen in some sockopts

[Sasha Levin]

From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>

[ Upstream commit 5960cefab9df76600a1a7d4ff592c59e14616e88 ]

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@xxxxxxxxxx>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 net/sctp/socket.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 1c08d86efe94..978fc7d1cf53 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3485,6 +3485,8 @@ static int sctp_setsockopt_hmac_ident(struct sock *sk,
 
 	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))
@@ -3523,6 +3525,11 @@ static int sctp_setsockopt_auth_key(struct sock *sk,
 
 	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))
@@ -3880,6 +3887,9 @@ static int sctp_setsockopt_reset_streams(struct sock *sk,
 
 	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))
-- 
2.11.0