[PATCH] accel/ethosu: fix IFM region index out-of-bounds in command stream parser

[Muhammad Bilal <meatuni001@gmail.com>]

NPU_SET_IFM_REGION extracts the region index with param & 0x7f, giving
a maximum value of 127. However region_size[] and output_region[] in
struct ethosu_validated_cmdstream_info are both sized to
NPU_BASEP_REGION_MAX (8), giving valid indices [0..7].

Every other region assignment in the same switch uses param & 0x7:
  NPU_SET_OFM_REGION:  st.ofm.region  = param & 0x7;
  NPU_SET_IFM2_REGION: st.ifm2.region = param & 0x7;
  NPU_SET_WEIGHT_REGION: st.weight[0].region = param & 0x7;
  NPU_SET_SCALE_REGION:  st.scale[0].region  = param & 0x7;

The 0x7f mask on IFM is inconsistent and appears to be a typo.

feat_matrix_length() and calc_sizes() use the region index directly
as an array subscript into the kzalloc'd info struct:
  info->region_size[fm->region] = max(...);

A userspace caller supplying NPU_SET_IFM_REGION with param > 7 causes
a write up to 127*8 = 1016 bytes past the start of region_size[],
corrupting adjacent kernel heap data.

Fix by applying the same & 0x7 mask used by all other region
assignments.

Fixes: 5a5e9c0228e6 ("accel: Add Arm Ethos-U NPU driver")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
 drivers/accel/ethosu/ethosu_gem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/accel/ethosu/ethosu_gem.c b/drivers/accel/ethosu/ethosu_gem.c
index f526f4aedffd..80d4bc21c28f 100644
--- a/drivers/accel/ethosu/ethosu_gem.c
+++ b/drivers/accel/ethosu/ethosu_gem.c
@@ -466,7 +466,7 @@ static int ethosu_gem_cmdstream_copy_and_validate(struct drm_device *ddev,
 			st.ifm.broadcast = param;
 			break;
 		case NPU_SET_IFM_REGION:
-			st.ifm.region = param & 0x7f;
+			st.ifm.region = param & 0x7;
 			break;
 		case NPU_SET_IFM_WIDTH0_M1:
 			st.ifm.width0 = param;
-- 
2.53.0