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SubjectRe: [PATCH 1/2] Fix printk() on ERR_PTR()
On Sun, 10 May 2015 21:42:15 +0200 Richard Weinberger <richard@nod.at> wrote:

> vbin_printf() checks whether the provided pointer is larger
> than -PAGE_SIZE such that it does not explode on ERR_PTR() pointers.
> printk() does not.
>
> Let's add this check also to the printk() code such that
> trace_printk() and printk() are consistent again.
>
> ..
>
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -511,7 +511,8 @@ char *string(char *buf, char *end, const char *s, struct printf_spec spec)
> {
> int len, i;
>
> - if ((unsigned long)s < PAGE_SIZE)
> + if ((unsigned long)s > (unsigned long)-PAGE_SIZE ||

hm, PAGE_SIZE has type ulong, so is the cast needed?

> + (unsigned long)s < PAGE_SIZE)

This would be a place for

if (!within(PAGE_SIZE, (unsigned long)s, -PAGE_SIZE))
s = "(null)";

I'm counting at least five implementations of within(), not all the same.

Maybe. Both the lower and upper bounds will sometimes want inclusive
semantics, sometimes exclusive.



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