Re: [PATCH] mm: Fail when offset == num in first check of vm_map_pages_zero()

From: Souptick Joarder <jrdr.linux@gmail.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: "Matthew Wilcox" <willy@infradead.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	"Huang Ying" <ying.huang@intel.com>,
	"open list" <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH] mm: Fail when offset == num in first check of vm_map_pages_zero()
Date: Wed, 29 May 2019 12:39:27 +0530	[thread overview]
Message-ID: <CAFqt6zZ0SHXddLoQMoO3LHT=50Br0x4r3Wn4XviypRxRUtn9zQ@mail.gmail.com> (raw)
In-Reply-To: <20190528193004.GA7744@gmail.com>

On Wed, May 29, 2019 at 1:38 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> If the user asks us for offset == num, we should already fail in the
> first check, i.e. the one testing for offsets beyond the object.
>
> At the moment, we are failing on the second test anyway,
> since count cannot be 0. Still, to agree with the comment of the first
> test, we should first there.

I think, we need to cc linux-mm.
>
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
> ---
>  mm/memory.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index ddf20bd0c317..74cf8b0ce353 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1547,7 +1547,7 @@ static int __vm_map_pages(struct vm_area_struct *vma, struct page **pages,
>         int ret, i;
>
>         /* Fail if the user requested offset is beyond the end of the object */
> -       if (offset > num)
> +       if (offset >= num)
>                 return -ENXIO;
>
>         /* Fail if the user requested size exceeds available object size */
> --
> 2.17.1
>