drm: add __user attribute to ptr_to_compat()

The ptr_to_compat() call takes a "void __user *", so cast
the compat drm calls that use it to avoid the following
warnings from sparse:

drivers/gpu/drm/drm_ioc32.c:188:39: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/drm_ioc32.c:188:39:    expected void [noderef] <asn:1>*uptr
drivers/gpu/drm/drm_ioc32.c:188:39:    got void *[addressable] [assigned] handle
drivers/gpu/drm/drm_ioc32.c:529:41: warning: incorrect type in argument 1 (different address spaces)
drivers/gpu/drm/drm_ioc32.c:529:41:    expected void [noderef] <asn:1>*uptr
drivers/gpu/drm/drm_ioc32.c:529:41:    got void *[addressable] [assigned] handle

Cc: stable@vger.kernel.org
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190301120046.26961-1-ben.dooks@codethink.co.uk

drivers/gpu/drm/drm_ioc32.c

@@ -185,7 +185,7 @@ static int compat_drm_getmap(struct file *file, unsigned int cmd,
 	m32.size = map.size;
 	m32.type = map.type;
 	m32.flags = map.flags;
-	m32.handle = ptr_to_compat(map.handle);
+	m32.handle = ptr_to_compat((void __user *)map.handle);
 	m32.mtrr = map.mtrr;
 	if (copy_to_user(argp, &m32, sizeof(m32)))
 		return -EFAULT;
@@ -216,7 +216,7 @@ static int compat_drm_addmap(struct file *file, unsigned int cmd,
 
 	m32.offset = map.offset;
 	m32.mtrr = map.mtrr;
-	m32.handle = ptr_to_compat(map.handle);
+	m32.handle = ptr_to_compat((void __user *)map.handle);
 	if (map.handle != compat_ptr(m32.handle))
 		pr_err_ratelimited("compat_drm_addmap truncated handle %p for type %d offset %x\n",
 				   map.handle, m32.type, m32.offset);
@@ -526,7 +526,7 @@ static int compat_drm_getsareactx(struct file *file, unsigned int cmd,
 	if (err)
 		return err;
 
-	req32.handle = ptr_to_compat(req.handle);
+	req32.handle = ptr_to_compat((void __user *)req.handle);
 	if (copy_to_user(argp, &req32, sizeof(req32)))
 		return -EFAULT;