drm/amdgpu: refine amdgpu_fru_get_product_info

1. eliminate potential array index out of bounds.
2. return meaningful value for failure.
Signed-off-by: Jiansong Chen <Jiansong.Chen@amd.com>
Reviewed-by: Jack Gui <Jack.Gui@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_fru_eeprom.c

@@ -101,7 +101,8 @@ static int amdgpu_fru_read_eeprom(struct amdgpu_device *adev, uint32_t addrptr,
 int amdgpu_fru_get_product_info(struct amdgpu_device *adev)
 {
 	unsigned char buff[34];
-	int addrptr = 0, size = 0;
+	int addrptr, size;
+	int len;
 
 	if (!is_fru_eeprom_supported(adev))
 		return 0;
@@ -109,7 +110,7 @@ int amdgpu_fru_get_product_info(struct amdgpu_device *adev)
 	/* If algo exists, it means that the i2c_adapter's initialized */
 	if (!adev->pm.smu_i2c.algo) {
 		DRM_WARN("Cannot access FRU, EEPROM accessor not initialized");
-		return 0;
+		return -ENODEV;
 	}
 
 	/* There's a lot of repetition here. This is due to the FRU having
@@ -128,7 +129,7 @@ int amdgpu_fru_get_product_info(struct amdgpu_device *adev)
 	size = amdgpu_fru_read_eeprom(adev, addrptr, buff);
 	if (size < 1) {
 		DRM_ERROR("Failed to read FRU Manufacturer, ret:%d", size);
-		return size;
+		return -EINVAL;
 	}
 
 	/* Increment the addrptr by the size of the field, and 1 due to the
@@ -138,43 +139,45 @@ int amdgpu_fru_get_product_info(struct amdgpu_device *adev)
 	size = amdgpu_fru_read_eeprom(adev, addrptr, buff);
 	if (size < 1) {
 		DRM_ERROR("Failed to read FRU product name, ret:%d", size);
-		return size;
+		return -EINVAL;
 	}
 
+	len = size;
 	/* Product name should only be 32 characters. Any more,
 	 * and something could be wrong. Cap it at 32 to be safe
 	 */
-	if (size > 32) {
+	if (len >= sizeof(adev->product_name)) {
 		DRM_WARN("FRU Product Number is larger than 32 characters. This is likely a mistake");
-		size = 32;
+		len = sizeof(adev->product_name) - 1;
 	}
 	/* Start at 2 due to buff using fields 0 and 1 for the address */
-	memcpy(adev->product_name, &buff[2], size);
-	adev->product_name[size] = '\0';
+	memcpy(adev->product_name, &buff[2], len);
+	adev->product_name[len] = '\0';
 
 	addrptr += size + 1;
 	size = amdgpu_fru_read_eeprom(adev, addrptr, buff);
 	if (size < 1) {
 		DRM_ERROR("Failed to read FRU product number, ret:%d", size);
-		return size;
+		return -EINVAL;
 	}
 
+	len = size;
 	/* Product number should only be 16 characters. Any more,
 	 * and something could be wrong. Cap it at 16 to be safe
 	 */
-	if (size > 16) {
+	if (len >= sizeof(adev->product_number)) {
 		DRM_WARN("FRU Product Number is larger than 16 characters. This is likely a mistake");
-		size = 16;
+		len = sizeof(adev->product_number) - 1;
 	}
-	memcpy(adev->product_number, &buff[2], size);
-	adev->product_number[size] = '\0';
+	memcpy(adev->product_number, &buff[2], len);
+	adev->product_number[len] = '\0';
 
 	addrptr += size + 1;
 	size = amdgpu_fru_read_eeprom(adev, addrptr, buff);
 
 	if (size < 1) {
 		DRM_ERROR("Failed to read FRU product version, ret:%d", size);
-		return size;
+		return -EINVAL;
 	}
 
 	addrptr += size + 1;
@@ -182,18 +185,19 @@ int amdgpu_fru_get_product_info(struct amdgpu_device *adev)
 
 	if (size < 1) {
 		DRM_ERROR("Failed to read FRU serial number, ret:%d", size);
-		return size;
+		return -EINVAL;
 	}
 
+	len = size;
 	/* Serial number should only be 16 characters. Any more,
 	 * and something could be wrong. Cap it at 16 to be safe
 	 */
-	if (size > 16) {
+	if (len >= sizeof(adev->serial)) {
 		DRM_WARN("FRU Serial Number is larger than 16 characters. This is likely a mistake");
-		size = 16;
+		len = sizeof(adev->serial) - 1;
 	}
-	memcpy(adev->serial, &buff[2], size);
-	adev->serial[size] = '\0';
+	memcpy(adev->serial, &buff[2], len);
+	adev->serial[len] = '\0';
 
 	return 0;
 }