On (06/25/15 00:55), Seymour, Shane M wrote:
> Changed the documentation to allow sprintf() for small
> single values and explicitly say snprintf() must never be used in
> a show function to format data to be returned to user space.
>
> Change based on a discussion about the patch
> st: convert DRIVER_ATTR macros to DRIVER_ATTR_RO
>
> Suggested-by: Greg Kroah-Hartman <[email protected]>
> Signed-off-by: Shane Seymour <[email protected]>
> ---
> --- a/Documentation/filesystems/sysfs.txt 2015-06-22 14:18:40.278620871
> -0500
> +++ b/Documentation/filesystems/sysfs.txt 2015-06-24 13:42:21.344446532
> -0500
> @@ -212,7 +212,9 @@ Other notes:
> - show() methods should return the number of bytes printed into the
> buffer. This is the return value of scnprintf().
>
> -- show() should always use scnprintf().
> +- show() must not use snprintf() when formatting a value to be
> + returned to user space. For small single values you can use
> + sprintf() otherwise you must use scnprintf().
Well, a single value can easily overflow
sprintf(buf, "%s", dev->large_value);
Probably the wording better be "if you guarantee that overflow will
never happen, then you can use ...".
-ss
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