linux-kernel - Re: [PATCH, REGRESSION v4] mm: make apply_to_page

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Date:	Fri, 22 Jan 2016 13:49:58 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Mika Penttilä <mika.penttila@...tfour.com>
cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Pekka Enberg <penberg@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH, REGRESSION v4] mm: make apply_to_page_range more
 robust

On Fri, 22 Jan 2016, Mika Penttilä wrote:

> diff --git a/mm/memory.c b/mm/memory.c
> index 30991f8..9178ee6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1871,7 +1871,9 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
>         unsigned long end = addr + size;
>         int err;
>  
> -       BUG_ON(addr >= end);
> +       if (WARN_ON(addr >= end))
> +               return -EINVAL;
> +
>         pgd = pgd_offset(mm, addr);
>         do {
>                 next = pgd_addr_end(addr, end);

This would be fine as a second patch in a 2-patch series.  The first patch 
should fix change_memory_common() for numpages == 0 by returning without 
ever calling this function and triggering the WARN_ON().  Let's fix the 
problem.