sctp: add a ceiling to optlen in some sockopts

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>

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 54c0467..022b94f 100644 (file)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3498,6 +3498,8 @@ 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))
@@ -3536,6 +3538,11 @@ 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))
@@ -3893,6 +3900,9 @@ 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))