Re: [PATCH] Ensure that walk_page_range()'s start and end are page-aligned

["Michal Nazarewicz" <mina86@mina86.com>]

On Fri, 10 Feb 2012 20:39:56 +0100, Dan Smith <danms@us.ibm.com> wrote:
> The inner function walk_pte_range() increments "addr" by PAGE_SIZE after

Commit message says about walk_pte_range() but commit changes walk_page_range().

> 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

So why not change the condition to addr < end?

> 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.
>
> Signed-off-by: Dan Smith <danms@us.ibm.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  mm/pagewalk.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> index 2f5cf10..9242bfc 100644
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -196,6 +196,8 @@ int walk_page_range(unsigned long addr, unsigned long end,
>  	if (addr >= end)
>  		return err;
>+	VM_BUG_ON((addr & ~PAGE_MASK) || (end & ~PAGE_MASK));
> +
>  	if (!walk->mm)
>  		return -EINVAL;
>


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..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
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