From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f198.google.com (mail-pl1-f198.google.com [209.85.214.198]) by kanga.kvack.org (Postfix) with ESMTP id 8F7A38E0002 for ; Thu, 3 Jan 2019 10:14:00 -0500 (EST) Received: by mail-pl1-f198.google.com with SMTP id b24so25608069pls.11 for ; Thu, 03 Jan 2019 07:14:00 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id c191si499116pfg.72.2019.01.03.07.13.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 03 Jan 2019 07:13:59 -0800 (PST) Date: Thu, 3 Jan 2019 16:13:57 +0100 From: Michal Hocko Subject: Re: [PATCH 1/3] mm/vmalloc: fix size check for remap_vmalloc_range_partial() Message-ID: <20190103151357.GR31793@dhcp22.suse.cz> References: <20190103145954.16942-1-rpenyaev@suse.de> <20190103145954.16942-2-rpenyaev@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190103145954.16942-2-rpenyaev@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Roman Penyaev Cc: Andrew Morton , Andrey Ryabinin , Joe Perches , "Luis R. Rodriguez" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org 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 > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Andrey Ryabinin > Cc: Joe Perches > Cc: "Luis R. Rodriguez" > 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