On Fri, 24 Feb 2012 11:19:25 -0800
Dan Smith <danms@xxxxxxxxxx> wrote:
>
> ...
>
> The inner function walk_pte_range() increments "addr" by PAGE_SIZE after
> each pte is processed, and only exits the loop if the result is equal to
> "end". Current, if either (or both of) the starting or ending addresses
> passed to walk_page_range() are not page-aligned, then we will never
> satisfy that exit condition and begin calling the pte_entry handler with
> bad data.
>
> To be sure that we will land in the right spot, this patch checks that
> both "addr" and "end" are page-aligned in walk_page_range() before starting
> the traversal.
>
> ...
>
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -196,6 +196,11 @@ int walk_page_range(unsigned long addr, unsigned long end,
> if (addr >= end)
> return err;
>
> + if (WARN_ONCE((addr & ~PAGE_MASK) || (end & ~PAGE_MASK),
> + "address range is not page-aligned")) {
> + return -EINVAL;
> + }
> +
> if (!walk->mm)
> return -EINVAL;
Well... why should we apply the patch? Is there some buggy code which
is triggering the problem? Do you intend to write some buggy code to
trigger the problem? ;)
IOW, what benefit is there to this change?
Also, as it's a developer-only thing we should arrange for the overhead
to vanish when CONFIG_DEBUG_VM=n?
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