media: staging: atomisp: Check return value from compat_alloc_user_space

If something gets wrong, return, instead of trying to
convert from a NULL pointer.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/atomisp/pci/atomisp_compat_ioctl32.c

@@ -863,6 +863,8 @@ static long atomisp_do_compat_ioctl(struct file *file,
 				 sizeof(struct atomisp_morph_table) +
 				 sizeof(struct atomisp_dis_coefficients) +
 				 sizeof(struct atomisp_dvs_6axis_config) : 0));
+	if (!karg)
+		return -ENOMEM;
 
 	/* First, convert the command. */
 	switch (cmd) {