Re: [PATCH] mm: as the same logic with queue_pages_range

From: Matthew Wilcox <willy@infradead.org>
To: Edward AD <eadavis@sina.com>
Cc: syzbot+b591856e0f0139f83023@syzkaller.appspotmail.com,
	akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] mm: as the same logic with queue_pages_range
Date: Wed, 6 Sep 2023 13:06:48 +0100	[thread overview]
Message-ID: <ZPhrWDYL+JfI6upH@casper.infradead.org> (raw)
In-Reply-To: <20230906061902.591996-1-eadavis@sina.com>

On Wed, Sep 06, 2023 at 02:19:02PM +0800, Edward AD wrote:
> Only dealwith queue_pages_range locked vmas.

What?

> Signed-off-by: Edward AD <eadavis@sina.com>
> ---
>  mm/mempolicy.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 42b5567e3773..13050b968479 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1342,6 +1342,8 @@ static long do_mbind(unsigned long start, unsigned long len,
>  	vma_iter_init(&vmi, mm, start);
>  	prev = vma_prev(&vmi);
>  	for_each_vma_range(vmi, vma, end) {
> +		if (!vma || start < vma->vm_start)
> +			continue;

#define for_each_vma_range(__vmi, __vma, __end)                         \
        while (((__vma) = vma_find(&(__vmi), (__end))) != NULL)

How can this produce a vma that is either NULL or has a vm_start after start?