[PATCH v2 4/4] drm/i915/guc: Verify hwconfig blob matches supported format

[Jordan Justen]

i915_drm.h now defines the format of the returned
DRM_I915_QUERY_HWCONFIG_BLOB query item. Since i915 receives this from
the black box GuC software, it should verify that the data matches
that format before sending it to user-space.

The verification makes a single simple pass through the blob contents,
so this verification step should not add a significant amount of init
time to i915.

Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
---
 .../gpu/drm/i915/gt/uc/intel_guc_hwconfig.c   | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_hwconfig.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_hwconfig.c
index ce6088f112d4..6208246d4209 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_hwconfig.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_hwconfig.c
@@ -71,6 +71,29 @@ static int guc_hwconfig_discover_size(struct intel_guc_hwconfig *hwconfig)
 	return 0;
 }
 
+static int verify_hwconfig_blob(const struct intel_guc_hwconfig *hwconfig)
+{
+	struct drm_i915_query_hwconfig_blob_item *pos;
+	u32 remaining;
+
+	if (hwconfig->size % 4 != 0 || hwconfig->ptr == NULL)
+		return -EINVAL;
+
+	pos = hwconfig->ptr;
+	remaining = (hwconfig->size / 4);
+	while (remaining > 0) {
+		if (remaining < 2)
+			return -EINVAL;
+		if (pos->length > remaining - 2)
+			return -EINVAL;
+		remaining -= 2 + pos->length;
+		pos = (void *)&pos->data[pos->length];
+	}
+
+	DRM_INFO("hwconfig blob format appears valid\n");
+	return 0;
+}
+
 static int guc_hwconfig_fill_buffer(struct intel_guc_hwconfig *hwconfig)
 {
 	struct intel_guc *guc = hwconfig_to_guc(hwconfig);
@@ -91,6 +114,12 @@ static int guc_hwconfig_fill_buffer(struct intel_guc_hwconfig *hwconfig)
 	if (ret >= 0)
 		memcpy(hwconfig->ptr, vaddr, hwconfig->size);
 
+	if (verify_hwconfig_blob(hwconfig)) {
+		DRM_ERROR("Ignoring invalid hwconfig blob received from "
+			  "GuC!\n");
+		return -EINVAL;
+	}
+
 	i915_vma_unpin_and_release(&vma, I915_VMA_RELEASE_MAP);
 
 	return ret;
-- 
2.34.1