[PATCH] efi_loader: capsule: detect possible ESP device path

[Dan Carpenter]

On Wed, May 08, 2024 at 07:24:01PM +0800, Weizhao Ouyang wrote:
> diff --git a/lib/efi_loader/efi_capsule.c b/lib/efi_loader/efi_capsule.c
> index de0d49ebebda..919e3cba071b 100644
> --- a/lib/efi_loader/efi_capsule.c
> +++ b/lib/efi_loader/efi_capsule.c
> @@ -922,6 +922,105 @@ static bool device_is_present_and_system_part(struct efi_device_path *dp)
>  	return true;
>  }
>  
> +/**
> + * get_esp_from_boot_option_file_path - get the expand device path
> + *
> + * Get a possible efi system partition by expanding a boot option
> + * file path.
> + *
> + * @boot_dev	The device path pointing to a boot option
> + * Return:	The full ESP device path or NULL if fail
> + */
> +static struct efi_device_path *get_esp_from_boot_option_file_path(struct efi_device_path *boot_dev)
> +{
> +	efi_status_t ret = EFI_SUCCESS;
> +	efi_handle_t handle;
> +	struct efi_device_path *dp = boot_dev;
> +	struct efi_device_path *full_path = NULL;
> +
> +	ret = EFI_CALL(efi_locate_device_path(&efi_simple_file_system_protocol_guid,
> +					      &dp,
> +					      &handle));
> +	if (ret != EFI_SUCCESS)
> +		ret = EFI_CALL(efi_locate_device_path(&efi_block_io_guid, &dp, &handle));
> +
> +	/* Expand Media Device Path */
> +	if (ret == EFI_SUCCESS && EFI_DP_TYPE(dp, END, END)) {

Flip this around.  Always do failure handling.  Never do success
handling.  full_path is always NULL.  Just return that.  Delete
the variable.

	if (ret != EFI_SUCCESS ||
	    !EFI_DP_TYPE(dp, END, END))
		return NULL;


> +		struct efi_device_path *temp_dp;
> +		struct efi_block_io *block_io;
> +		void *buffer;
> +		efi_handle_t *simple_file_system_handle;
> +		efi_uintn_t number_handles, index;
> +		u32 size;
> +		u32 temp_size;
> +
> +		temp_dp = boot_dev;
> +		ret = EFI_CALL(efi_locate_device_path(&efi_simple_file_system_protocol_guid,
> +						      &temp_dp,
> +						      &handle));
> +		/*
> +		 * For device path pointing to simple file system, it only expands to one
> +		 * full path
> +		 */
> +		if (ret == EFI_SUCCESS && EFI_DP_TYPE(temp_dp, END, END)) {

"Always" was hyperbole.  This success handling is fine.

> +			if (device_is_present_and_system_part(temp_dp))
> +				return temp_dp;
> +		}
> +
> +		/*
> +		 * For device path only pointing to the removable device handle, try to
> +		 * search all its children handles
> +		 */
> +		ret = EFI_CALL(efi_locate_device_path(&efi_block_io_guid, &temp_dp, &handle));

ret is not used.  Delete.

> +		EFI_CALL(efi_connect_controller(handle, NULL, NULL, true));
> +
> +		/* Align with edk2, issue a dummy read to the device to check the device change */
> +		ret = EFI_CALL(efi_handle_protocol(handle, &efi_block_io_guid, (void **)&block_io));
> +		if (ret == EFI_SUCCESS) {

	if (ret != EFI_SUCCESS)
		return NULL;

> +			buffer = memalign(block_io->media->io_align, block_io->media->block_size);
> +			if (buffer) {

	if (!buffer)
		return NULL;


> +				ret = EFI_CALL(block_io->read_blocks(block_io,
> +								     block_io->media->media_id,
> +								     0,
> +								     block_io->media->block_size,
> +								     buffer));

Delete the unused "ret = " assignment.

> +				free(buffer);
> +			} else {
> +				return full_path;
> +			}
> +		} else {
> +			return full_path;
> +		}
> +
> +		/* detect the default boot file from removable media */
> +		size = efi_dp_size(boot_dev) - sizeof(struct efi_device_path);
> +		EFI_CALL(efi_locate_handle_buffer(BY_PROTOCOL,
> +						  &efi_simple_file_system_protocol_guid,
> +						  NULL,
> +						  &number_handles,
> +						  &simple_file_system_handle));
> +		for (index = 0; index < number_handles; index++) {
> +			EFI_CALL(efi_handle_protocol(simple_file_system_handle[index],
> +						     &efi_guid_device_path,
> +						     (void **)&temp_dp));
> +
> +			log_debug("Search ESP %pD\n", temp_dp);
> +			temp_size = efi_dp_size(temp_dp) - sizeof(struct efi_device_path);
> +			if (size <= temp_size && !memcmp(temp_dp, boot_dev, size)) {
> +				if (device_is_present_and_system_part(temp_dp)) {

You could combine these conditions:

		if (size <= temp_size &&
		    memcmp(temp_dp, boot_dev, size) == 0 &&
		    device_is_present_and_system_part(temp_dp)) {
			efi_free_pool(simple_file_system_handle);
			return temp_dp;
		}


> +					efi_free_pool(simple_file_system_handle);
> +					return temp_dp;
> +				}
> +			}
> +		}
> +
> +		if (simple_file_system_handle)
> +			efi_free_pool(simple_file_system_handle);
> +	}
> +
> +	return full_path;
> +}
> +
>  /**
>   * find_boot_device - identify the boot device
>   *
> @@ -938,6 +1037,7 @@ static efi_status_t find_boot_device(void)
>  	int i, num;
>  	struct efi_simple_file_system_protocol *volume;
>  	struct efi_device_path *boot_dev = NULL;
> +	struct efi_device_path *full_path = NULL;

No need to initialize this to NULL, it disables static checker warnings
for uninitialized variables so it can lead to bugs.

>  	efi_status_t ret;
>  
>  	/* find active boot device in BootNext */
> @@ -961,8 +1061,14 @@ static efi_status_t find_boot_device(void)
>  			if (device_is_present_and_system_part(boot_dev)) {
>  				goto found;
>  			} else {
> -				efi_free_pool(boot_dev);
> -				boot_dev = NULL;
> +				full_path = get_esp_from_boot_option_file_path(boot_dev);
> +				if (full_path) {
> +					boot_dev = full_path;

Later, we free full_path but do we ever free the original boot_dev?

> +					goto found;
> +				} else {
> +					efi_free_pool(boot_dev);
> +					boot_dev = NULL;
> +				}

Better to delete indenting where you can:

			full_path = get_esp_from_boot_option_file_path(boot_dev);
			if (full_path) {
				boot_dev = full_path;
				goto found;
			}
			efi_free_pool(boot_dev);
			boot_dev = NULL;

regards,
dan carpenter