[PATCH] media: mali-c55: Fix unaligned access of AEC histogram zone weights

[PATCH] media: mali-c55: Fix unaligned access of AEC histogram zone weights

[David Carlier]

mali_c55_params_aexp_hist_weights() packs the 225 per-zone u8 weights
into the ISP registers four at a time by casting the zone_weights array
to u32 and dereferencing it. The array sits at offset 10 within the
parameter block, so it is only 2-byte aligned: the u32 access is
unaligned, which is undefined behaviour and can fault on strict-align
configurations or once the loop is auto-vectorised.

The cast also reads the four weights in host byte order before they are
written to the little-endian register, so on big-endian hosts the four
weights packed into each register end up in the wrong byte lanes.

Read the weights with get_unaligned_le32() instead, which is both
alignment-safe and fixes the byte order regardless of host endianness.

Fixes: d5f281f3dd29 ("media: mali-c55: Add Mali-C55 ISP driver")
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 drivers/media/platform/arm/mali-c55/mali-c55-params.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-params.c b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
index de0e9d898..1aaf64dde 100644
--- a/drivers/media/platform/arm/mali-c55/mali-c55-params.c
+++ b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
@@ -6,6 +6,7 @@
  */
 #include <linux/media/arm/mali-c55-config.h>
 #include <linux/pm_runtime.h>
+#include <linux/unaligned.h>
 
 #include <media/media-entity.h>
 #include <media/v4l2-dev.h>
@@ -203,7 +204,7 @@ mali_c55_params_aexp_hist_weights(struct mali_c55 *mali_c55,
 	 * of overwriting other registers.
 	 */
 	for (unsigned int i = 0; i < 56; i++) {
-		val = ((u32 *)params->zone_weights)[i]
+		val = get_unaligned_le32(&params->zone_weights[i * 4])
 			    & MALI_C55_AEXP_HIST_ZONE_WEIGHT_MASK;
 		addr = base + MALI_C55_AEXP_HIST_ZONE_WEIGHTS_OFFSET + (4 * i);
 
-- 
2.53.0