Struct uvc_frame and interval (u32*) are packaged together on streaming->formats on a single contiguous allocation. Right now they 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@xxxxxxxxxxxx> --- This is better than 3 allocations, and do not have any performance penalty. I have tried this patch printing the size and the address of the pointers in the old and the new mode, and it looks the same. [ 2.235223] drivers/media/usb/uvc/uvc_driver.c:694 uvc_parse_streaming 432 [ 2.235249] drivers/media/usb/uvc/uvc_driver.c:704 uvc_parse_streaming 432 [ 2.235256] drivers/media/usb/uvc/uvc_driver.c:714 uvc_parse_streaming 00000000d32087cc 00000000d3803788 [ 2.235265] drivers/media/usb/uvc/uvc_driver.c:720 uvc_parse_streaming 00000000d32087cc 00000000d3803788 --- Changes in v2: Thanks Laurent. - Enforce alignment during allocation instead of using __aligned() macros. - Link to v1: https://lore.kernel.org/r/20230501-uvc-align-v1-1-0f713e4b84c3@xxxxxxxxxxxx --- drivers/media/usb/uvc/uvc_driver.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c index 7aefa76a42b31..7d9844ba3b205 100644 --- a/drivers/media/usb/uvc/uvc_driver.c +++ b/drivers/media/usb/uvc/uvc_driver.c @@ -663,16 +663,26 @@ static int uvc_parse_streaming(struct uvc_device *dev, goto error; } - size = nformats * sizeof(*format) + nframes * sizeof(*frame) - + nintervals * sizeof(*interval); + /* + * 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->format = format; streaming->nformats = nformats; --- base-commit: 58390c8ce1bddb6c623f62e7ed36383e7fa5c02f change-id: 20230501-uvc-align-6ff202b68dab Best regards, -- Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
