drm/amdgpu/vcn3: Prevent OOB reads when parsing dec msg

From Benjamin Cheng
638e48ee39d0f2af9336f917a6f5d6692dd64d93 in linux-6.18.y/6.18.32
b193019860d61e92da395eae2011f2f6716b182f in mainline linux

sys/dev/pci/drm/amd/amdgpu/vcn_v3_0.c

@@ -1908,7 +1908,7 @@ static int vcn_v3_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
 {
 	struct ttm_operation_ctx ctx = { false, false };
 	struct amdgpu_bo_va_mapping *map;
-	uint32_t *msg, num_buffers;
+	uint32_t *msg, num_buffers, len_dw;
 	struct amdgpu_bo *bo;
 	uint64_t start, end;
 	unsigned int i;
@@ -1929,6 +1929,11 @@ static int vcn_v3_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
 		return -EINVAL;
 	}
 
+	if (end - addr < 16) {
+		DRM_ERROR("VCN messages must be at least 4 DWORDs!\n");
+		return -EINVAL;
+	}
+
 	bo->flags |= AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
 	amdgpu_bo_placement_from_domain(bo, bo->allowed_domains);
 	r = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
@@ -1945,8 +1950,8 @@ static int vcn_v3_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
 
 	msg = ptr + addr - start;
 
-	/* Check length */
 	if (msg[1] > end - addr) {
+		DRM_ERROR("VCN message header does not fit in BO!\n");
 		r = -EINVAL;
 		goto out;
 	}
@@ -1954,7 +1959,16 @@ static int vcn_v3_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
 	if (msg[3] != RDECODE_MSG_CREATE)
 		goto out;
 
+	len_dw = msg[1] / 4;
 	num_buffers = msg[2];
+
+	/* Verify that all indices fit within the claimed length. Each index is 4 DWORDs */
+	if (num_buffers > len_dw || 6 + num_buffers * 4 > len_dw) {
+		DRM_ERROR("VCN message has too many buffers!\n");
+		r = -EINVAL;
+		goto out;
+	}
+
 	for (i = 0, msg = &msg[6]; i < num_buffers; ++i, msg += 4) {
 		uint32_t offset, size, *create;
 
@@ -1964,14 +1978,15 @@ static int vcn_v3_0_dec_msg(struct amdgpu_cs_parser *p, struct amdgpu_job *job,
 		offset = msg[1];
 		size = msg[2];
 
-		if (offset + size > end) {
+		if (size < 4 || offset + size > end - addr) {
+			DRM_ERROR("VCN message buffer exceeds BO bounds!\n");
 			r = -EINVAL;
 			goto out;
 		}
 
 		create = ptr + addr + offset - start;
 
-		/* H246, HEVC and VP9 can run on any instance */
+		/* H264, HEVC and VP9 can run on any instance */
 		if (create[0] == 0x7 || create[0] == 0x10 || create[0] == 0x11)
 			continue;