sctp: correct bounds check in sctp_setsockopt_auth_key

[ Upstream commit 328fc47ea0bcc27d9afa69c3ad6e52431cadd76c ]

The bonds check to prevent buffer overlflow was not exactly
right.  It still allowed overflow of up to 8 bytes which is
sizeof(struct sctp_authkey).

Since optlen is already checked against the size of that struct,
we are guaranteed not to cause interger overflow either.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index e62aafc320c265110373aead79c17cf02be67792..68681fee61a6cafcb6046659d2106b4ee6656be3 100644 (file)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3054,7 +3054,7 @@ static int sctp_setsockopt_auth_key(struct sock *sk,
                goto out;
        }
 
-       if (authkey->sca_keylength > optlen) {
+       if (authkey->sca_keylength > optlen - sizeof(struct sctp_authkey)) {
                ret = -EINVAL;
                goto out;
        }