media: uvcvideo: Enforce alignment of frame and interval

Struct uvc_frame and interval (u32*) are packaged together on
streaming->formats on a single contiguous allocation.

Right now they are allocated right after uvc_format, without taking into
consideration their required alignment.

This is working fine because both structures have a field with a
pointer, but it will stop working when the sizeof() of any of those
structs is not a multiple of the sizeof(void*).

Enforce that alignment during the allocation.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20240404-uvc-align-v2-1-9e104b0ecfbd@chromium.org
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index d435b6a6c295d9def0dd0e86c487800e7d761e7e..13c2c11cfdf64d866a9fd3c0f24f07a7cbc11e40 100644 (file)
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -687,16 +687,26 @@ static int uvc_parse_streaming(struct uvc_device *dev,
                goto error;
        }
 
-       size = nformats * sizeof(*format) + nframes * sizeof(*frame)
+       /*
+        * Allocate memory for the formats, the frames and the intervals,
+        * plus any required padding to guarantee that everything has the
+        * correct alignment.
+        */
+       size = nformats * sizeof(*format);
+       size = ALIGN(size, __alignof__(*frame)) + nframes * sizeof(*frame);
+       size = ALIGN(size, __alignof__(*interval))
             + nintervals * sizeof(*interval);
+
        format = kzalloc(size, GFP_KERNEL);
-       if (format == NULL) {
+       if (!format) {
                ret = -ENOMEM;
                goto error;
        }
 
-       frame = (struct uvc_frame *)&format[nformats];
-       interval = (u32 *)&frame[nframes];
+       frame = (void *)format + nformats * sizeof(*format);
+       frame = PTR_ALIGN(frame, __alignof__(*frame));
+       interval = (void *)frame + nframes * sizeof(*frame);
+       interval = PTR_ALIGN(interval, __alignof__(*interval));
 
        streaming->formats = format;
        streaming->nformats = 0;