[kernel-hardening] Re: [PATCH V8 1/2] printk: remove tabular output for NULL pointer

[Joe Perches <joe@perches.com>]

On Thu, 2017-10-26 at 13:53 +1100, Tobin C. Harding wrote:
> Currently pointer() checks for a NULL pointer argument and then if so
> attempts to print "(null)" with _some_ standard width. This width cannot
> correctly be ascertained here because many of the printk specifiers
> print pointers of varying widths.

I believe this is not a good change.
Only pointers without a <foo> extension call pointer()

> Remove the attempt to print NULL pointers with a correct width.

the correct width for a %p is the default width.
The correct width for %p<foo> is unknown.

> Signed-off-by: Tobin C. Harding <me@tobin.cc>
> ---
>  lib/vsprintf.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 86c3385b9eb3..16a587aed40e 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1710,15 +1710,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
>  {
>  	const int default_width = 2 * sizeof(void *);
>  
> -	if (!ptr && *fmt != 'K') {
> -		/*
> -		 * Print (null) with the same width as a pointer so it makes
> -		 * tabular output look nice.
> -		 */
> -		if (spec.field_width == -1)
> -			spec.field_width = default_width;
> +	if (!ptr && *fmt != 'K')
>  		return string(buf, end, "(null)", spec);
> -	}
>  
>  	switch (*fmt) {
>  	case 'F':