Locking down U-Boot env with ENV_WRITEABLE_LIST

[Marek Vasut]

On 4/3/21 6:43 PM, Tim Harvey wrote:

Hi,

[...]

>>>> And those config options I had enabled in u-boot defconfig:
>>>>
>>>> CONFIG_CMD_ENV_CALLBACK=y
>>>> CONFIG_CMD_ENV_FLAGS=y
>>>> CONFIG_ENV_IS_NOWHERE=y
>>>> CONFIG_ENV_IS_IN_MMC=y
>>>> CONFIG_ENV_APPEND=y
>>>> CONFIG_ENV_WRITEABLE_LIST=y
>>>> CONFIG_ENV_ACCESS_IGNORE_FORCE=y
>>>
>>> Do you really define both ENV_IS_NOWHERE and ENV_IS_IN_MMC? From what
>>> I see if you define ENV_IS_NOWHERE none of the others will be used.
>>
>> Yes, having two ENV drivers is mandatory. One provides the base env (the
>> nowhere) and the other is used to import the filtered extras from
>> external env.
> 
> Enabling ENV_IS_NOWHERE does not work as you describe in my testing.
> I'm testing this with imx8mm_venice_defconfig on U-Boot 2021.01 and as
> soon as I define ENV_IS_NOWHERE then env_load is never called because
> when env_relocate is called env is not valid yet so env_set_default is
> called and env_load is 'never' called, thus mmc env is never loaded.
> This is all from
> https://elixir.bootlin.com/u-boot/v2021.01/source/env/common.c#L259

Maybe this [PATCH V3] env: Fix invalid env handling in env_init() patch 
is missing ?

[...]

>   /* Link Definitions */
>   #define CONFIG_LOADADDR                        0x40480000
>   #define CONFIG_SYS_LOAD_ADDR           CONFIG_LOADADDR''
> 
> With this configuration a blank env in flash results in the entire
> default env showing in an 'env print' (ie all the stuff from
> include/env_default.h 'default_environment') but as soon as I put an
> env in flash (ie saveenv) and reset now the only env is what was set
> via running code (ethaddr's fdtcontroladdr stdin/err/out). The only
> different I expected is that I expected the default env from
> include/env_default.h to be there on an initial boot with no valid mmc
> env.

Maybe the aforementioned patch is missing ?