From: Michal Hocko <mhocko@kernel.org>
To: Roman Penyaev <rpenyaev@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Joe Perches <joe@perches.com>,
"Luis R. Rodriguez" <mcgrof@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH 1/3] mm/vmalloc: fix size check for remap_vmalloc_range_partial()
Date: Thu, 3 Jan 2019 16:13:57 +0100 [thread overview]
Message-ID: <20190103151357.GR31793@dhcp22.suse.cz> (raw)
In-Reply-To: <20190103145954.16942-2-rpenyaev@suse.de>
On Thu 03-01-19 15:59:52, Roman Penyaev wrote:
> area->size can include adjacent guard page but get_vm_area_size()
> returns actual size of the area.
>
> This fixes possible kernel crash when userspace tries to map area
> on 1 page bigger: size check passes but the following vmalloc_to_page()
> returns NULL on last guard (non-existing) page.
Can this actually happen? I am not really familiar with all the callers
of this API but VM_NO_GUARD is not really used wildly in the kernel.
All I can see is kasan na arm64 which doesn't really seem to use it
for vmalloc.
So is the problem real or this is a mere cleanup?
> Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Joe Perches <joe@perches.com>
> Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Cc: stable@vger.kernel.org
> ---
> mm/vmalloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 871e41c55e23..2cd24186ba84 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2248,7 +2248,7 @@ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
> if (!(area->flags & VM_USERMAP))
> return -EINVAL;
>
> - if (kaddr + size > area->addr + area->size)
> + if (kaddr + size > area->addr + get_vm_area_size(area))
> return -EINVAL;
>
> do {
> --
> 2.19.1
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2019-01-03 15:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190103145954.16942-1-rpenyaev@suse.de>
2019-01-03 14:59 ` [PATCH 1/3] mm/vmalloc: fix size check for remap_vmalloc_range_partial() Roman Penyaev
2019-01-03 15:13 ` Michal Hocko [this message]
2019-01-03 19:27 ` Roman Penyaev
2019-01-03 19:40 ` Michal Hocko
2019-01-03 20:31 ` Roman Penyaev
2019-01-04 9:38 ` Michal Hocko
2019-01-04 10:21 ` Roman Penyaev
2019-01-04 10:28 ` Michal Hocko
2019-01-03 19:59 ` Michal Hocko
2019-01-04 11:06 ` Roman Penyaev
2019-01-11 19:19 ` Andrey Ryabinin
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