[PATCH 4.20 88/92] drm: Use array_size() when creating lease

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthew Wilcox <willy@xxxxxxxxxxxxx>

commit 69ef943dbc14b21987c79f8399ffea08f9a1b446 upstream.

Passing an object_count of sufficient size will make
object_count * 4 wrap around to be very small, then a later function
will happily iterate off the end of the object_ids array.  Using
array_size() will saturate at SIZE_MAX, the kmalloc() will fail and
we'll return an -ENOMEM to the norty userspace.

Fixes: 62884cd386b8 ("drm: Add four ioctls for managing drm mode object leases [v7]")
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v4.15+
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/drm_lease.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_lease.c
+++ b/drivers/gpu/drm/drm_lease.c
@@ -521,7 +521,8 @@ int drm_mode_create_lease_ioctl(struct d
 
 	object_count = cl->object_count;
 
-	object_ids = memdup_user(u64_to_user_ptr(cl->object_ids), object_count * sizeof(__u32));
+	object_ids = memdup_user(u64_to_user_ptr(cl->object_ids),
+			array_size(object_count, sizeof(__u32)));
 	if (IS_ERR(object_ids))
 		return PTR_ERR(object_ids);