[PATCH] media: sti: delta: use unaligned accessors for MJPEG SOF fields

[Runyu Xiao]

delta_mjpeg_read_header() scans a compressed MJPEG access unit byte by
byte and passes the bytes after an SOF marker to delta_mjpeg_read_sof().
The SOF parser then reads 16-bit big-endian fields directly from that
byte stream.

The SOF payload is not an aligned object. The marker scan can find the
payload at any byte position, and the SOF layout also puts frame_height
and frame_width after a one-byte sample_precision field. Those fields
therefore sit at odd offsets within the payload even when the payload
base happens to be 2-byte aligned.

Avoid casting the byte stream to __be16 pointers and use
get_unaligned_be16() for the SOF length, height, and width fields.

This issue was detected by our static analysis tool and confirmed by
manual audit. A focused UBSAN alignment validation of the same typed
load shape reported a misaligned __be16 access in delta_mjpeg_read_sof().

Fixes: 433ff5b4a29b ("[media] st-delta: add mjpeg support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Runyu Xiao <runyu.xiao@xxxxxxxxxx>
---
 drivers/media/platform/st/sti/delta/delta-mjpeg-hdr.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/st/sti/delta/delta-mjpeg-hdr.c b/drivers/media/platform/st/sti/delta/delta-mjpeg-hdr.c
index 90e5b2f72c82..849a5e118aec 100644
--- a/drivers/media/platform/st/sti/delta/delta-mjpeg-hdr.c
+++ b/drivers/media/platform/st/sti/delta/delta-mjpeg-hdr.c
@@ -4,6 +4,7 @@
  * Author: Hugues Fruchet <hugues.fruchet@xxxxxx> for STMicroelectronics.
  */
 
+#include <linux/unaligned.h>
 #include "delta.h"
 #include "delta-mjpeg.h"
 
@@ -48,13 +49,13 @@ static int delta_mjpeg_read_sof(struct delta_ctx *pctx,
 		goto err_no_more;
 
 	memset(header, 0, sizeof(*header));
-	header->length           = be16_to_cpu(*(__be16 *)(data + offset));
+	header->length           = get_unaligned_be16(data + offset);
 	offset += sizeof(u16);
 	header->sample_precision = *(u8 *)(data + offset);
 	offset += sizeof(u8);
-	header->frame_height     = be16_to_cpu(*(__be16 *)(data + offset));
+	header->frame_height     = get_unaligned_be16(data + offset);
 	offset += sizeof(u16);
-	header->frame_width      = be16_to_cpu(*(__be16 *)(data + offset));
+	header->frame_width      = get_unaligned_be16(data + offset);
 	offset += sizeof(u16);
 	header->nb_of_components = *(u8 *)(data + offset);
 	offset += sizeof(u8);
-- 
2.34.1