[PATCH 1/2] efi_firmware: set EFI capsule dfu_alt_info env explicitly

[Mattijs Korpershoek]

Hi Jon,

Thank you for the patch.

On lun., févr. 03, 2025 at 15:53, Jonathan Humphreys <j-humphreys at ti.com> wrote:

> The current implementation of EFI capsule update uses set_dfu_alt_info() to
> set the dfu_alt_info environment variable with the settings it requires.
> However, set_dfu_alt_info() is doing this for all DFU operations, even
> those unrelated to capsule update.
>
> Thus other uses of DFU, such as DFU boot which sets its own value for the
> dfu_alt_info environment variable, will have that setting overwritten with
> the capsule update setting. Similarly, any user defined value for the
> dfu_alt_info environment variable would get overwritten when any DFU
> operation was performed, including simply performing a "dfu 0 list"
> command.
>
> The solution is stop using the set_dfu_alt_info() mechanism to set the
> dfu_alt_info environment variable and instead explicitly set it to the
> capsule update's setting just before performing the capsule update's DFU
> operation, and then restore the environment variable back to its original
> value.
>
> This patch implements the explicit setting and restoring of the
> dfu_alt_info environment variable as part of the EFI capsule update
> operation.
>
> The fix is fully implemented in a subsequent patch that removes the capsule
> update dfu_alt_info support in set_dfu_alt_info().
>
> Signed-off-by: Jonathan Humphreys <j-humphreys at ti.com>
> ---
>  lib/efi_loader/efi_firmware.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> diff --git a/lib/efi_loader/efi_firmware.c b/lib/efi_loader/efi_firmware.c
> index 5a754c9cd03..d8b6d34ccab 100644
> --- a/lib/efi_loader/efi_firmware.c
> +++ b/lib/efi_loader/efi_firmware.c
> @@ -649,8 +649,10 @@ efi_status_t EFIAPI efi_firmware_fit_set_image(
>  	efi_status_t (*progress)(efi_uintn_t completion),
>  	u16 **abort_reason)
>  {
> +	int ret;
>  	efi_status_t status;
>  	struct fmp_state state = { 0 };
> +	char *orig_dfu_env;
>  
>  	EFI_ENTRY("%p %d %p %zu %p %p %p\n", this, image_index, image,
>  		  image_size, vendor_code, progress, abort_reason);
> @@ -663,9 +665,22 @@ efi_status_t EFIAPI efi_firmware_fit_set_image(
>  	if (status != EFI_SUCCESS)
>  		return EFI_EXIT(status);
>  
> +	orig_dfu_env = env_get("dfu_alt_info");
> +	ret = env_set("dfu_alt_info", update_info.dfu_string);
> +	if (ret) {
> +		pr_err("unable to set env variable \"dfu_alt_info\"!\n");

I could not find any other usage of pr_err() in this file so I think
we should use the log_err() instead of pr_err() here.

> +		return -EINVAL;
> +	}
> +
>  	if (fit_update(image))

Should we restore to orig_dfu_env in case fit_update() fails?
If not, why not? Maybe we can state this in the commit message or in a
code comment?

>  		return EFI_EXIT(EFI_DEVICE_ERROR);
>  
> +	ret = env_set("dfu_alt_info", orig_dfu_env);
> +	if (ret) {
> +		pr_err("unable to set env variable \"dfu_alt_info\"!\n");

pr_err() -> log_err()

> +		return -EINVAL;
> +	}
> +
>  	efi_firmware_set_fmp_state_var(&state, image_index);
>  
>  	return EFI_EXIT(EFI_SUCCESS);
> @@ -717,6 +732,7 @@ efi_status_t EFIAPI efi_firmware_raw_set_image(
>  	u8 dfu_alt_num;
>  	efi_status_t status;
>  	struct fmp_state state = { 0 };
> +	char *orig_dfu_env;
>  
>  	EFI_ENTRY("%p %d %p %zu %p %p %p\n", this, image_index, image,
>  		  image_size, vendor_code, progress, abort_reason);
> @@ -747,10 +763,23 @@ efi_status_t EFIAPI efi_firmware_raw_set_image(
>  		}
>  	}
>  
> +	orig_dfu_env = env_get("dfu_alt_info");
> +	ret = env_set("dfu_alt_info", update_info.dfu_string);
> +	if (ret) {
> +		pr_err("unable to set env variable \"dfu_alt_info\"!\n");

pr_err() -> log_err()

> +		return -EINVAL;
> +	}
> +
>  	if (dfu_write_by_alt(dfu_alt_num, (void *)image, image_size,
>  			     NULL, NULL))
>  		return EFI_EXIT(EFI_DEVICE_ERROR);
>  
> +	ret = env_set("dfu_alt_info", orig_dfu_env);
> +	if (ret) {
> +		pr_err("unable to set env variable \"dfu_alt_info\"!\n");

pr_err() -> log_err()

> +		return -EINVAL;
> +	}
> +
>  	efi_firmware_set_fmp_state_var(&state, image_index);
>  
>  	return EFI_EXIT(EFI_SUCCESS);
> -- 
> 2.34.1