[PATCH 5.4 020/121] media: uvcvideo: Enforce alignment of frame and interval

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

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

From: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>

[ Upstream commit c8931ef55bd325052ec496f242aea7f6de47dc9c ]

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@xxxxxxxxxxxx>
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240404-uvc-align-v2-1-9e104b0ecfbd@xxxxxxxxxxxx
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/media/usb/uvc/uvc_driver.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 0caa57a6782a..6d1a7e02da51 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -887,16 +887,26 @@ 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->format = format;
 	streaming->nformats = nformats;
-- 
2.43.0







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