[PATCH] env: mmc: Correct partition comparison in mmc_offset_try_partition

[Wolfgang Denk <wd@denx.de>]

Dear Hoyeonjiki Kim,

In message <20201112123026.458-1-jigi.kim@gmail.com> you wrote:
> The function mmc_offset_try_partition searches MMC partition to save the
> environment data by name.  However, it only compares the first word-size
> bytes (size of 'const char *'), which may make the function to find
> unintended partition.
>
> Correct the function not to partially compare the partition name with
> config "u-boot,mmc-env-partition".
>
> Fixes: c9e87ba66540 ("env: Save environment at the end of an MMC partition")
> Signed-off-by: Hoyeonjiki Kim <jigi.kim@gmail.com>
> Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
> ---
>  env/mmc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/env/mmc.c b/env/mmc.c
> index 4e67180b23..505f7aa2b8 100644
> --- a/env/mmc.c
> +++ b/env/mmc.c
> @@ -42,7 +42,7 @@ static inline int mmc_offset_try_partition(const char *str, int copy, s64 *val)
>  		if (ret < 0)
>  			return ret;
>  
> -		if (!strncmp((const char *)info.name, str, sizeof(str)))
> +		if (!strcmp((const char *)info.name, str))

This looks dangerous to me.  If the used length  sizeof(str) is not
correct, that should be fixed, but switching to strcmp() means we
may run into problems if the buffer is not NUL terminated.  Do we
have a guarantee here thai it always ist??  The fact that strncmp()
has been used before suggests otyherwise.

Please double-check.

Best regards,

Wolfgang Denk

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