RDMA/ucma: ucma_context reference leak in error path

commit ef95a90a upstream.

Validating input parameters should be done before getting the cm_id
otherwise it can leak a cm_id reference.

Fixes: 6a21dfc0 ("RDMA/ucma: Limit possible option size")
Signed-off-by: Shamir Rabinovitch <shamir.rabinovitch@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
[iwamatsu: Backported to 4.4, 4.9 and 4.14: adjust context]
Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/infiniband/core/ucma.c

@@ -1296,13 +1296,13 @@ static ssize_t ucma_set_option(struct ucma_file *file, const char __user *inbuf,
 	if (copy_from_user(&cmd, inbuf, sizeof(cmd)))
 		return -EFAULT;
 
+	if (unlikely(cmd.optlen > KMALLOC_MAX_SIZE))
+		return -EINVAL;
+
 	ctx = ucma_get_ctx(file, cmd.id);
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);
 
-	if (unlikely(cmd.optlen > KMALLOC_MAX_SIZE))
-		return -EINVAL;
-
 	optval = memdup_user((void __user *) (unsigned long) cmd.optval,
 			     cmd.optlen);
 	if (IS_ERR(optval)) {