Re: [PATCH v1 1/2] mmc-utils: Use memcpy instead of strncpy

[Ajay Garg]

Hi Bean.

> -               strncpy(lbuf, (char*)&ext_csd[EXT_CSD_FIRMWARE_VERSION], 8);
> +               memcpy(lbuf, (char*)&ext_csd[EXT_CSD_FIRMWARE_VERSION], 8);
> +               lbuf[8] = '\0';

Above copies exactly 8 bytes, without any regard to the sizes of
destination-buffer (lbuf) or source-buffer (ext_csd). Thus, there are
high chances of overflow/underflow/out-of-bounds.

If ext_csd contains, say a string 5 characters long, you would want to
copy 6 characters (5 for length, 1 for null-terminator).

I guess you are trying to copy as-many-bytes as possible to lbuf,
including the null-character.
Thus, strlcpy/strscpy should be used here.

Something like :

strlcpy(lbuf, (char*)&ext_csd[EXT_CSD_FIRMWARE_VERSION], sizeof(lbuf));
or
strscpy(lbuf, (char*)&ext_csd[EXT_CSD_FIRMWARE_VERSION], sizeof(lbuf));

Note that you do not need to worry about putting the null-terminator.
strlcpy/strscpy already take care of that for you.


Thanks and Regards,
Ajay