From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 915F6C433FE for ; Wed, 19 Jan 2022 11:17:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354092AbiASLRi (ORCPT ); Wed, 19 Jan 2022 06:17:38 -0500 Received: from foss.arm.com ([217.140.110.172]:54034 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354083AbiASLRh (ORCPT ); Wed, 19 Jan 2022 06:17:37 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C1945ED1; Wed, 19 Jan 2022 03:17:36 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.3.112]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 97B953F73D; Wed, 19 Jan 2022 03:17:34 -0800 (PST) Date: Wed, 19 Jan 2022 11:16:17 +0000 From: Mark Rutland To: Yury Norov Cc: Catalin Marinas , Will Deacon , Andrew Morton , Nicholas Piggin , Ding Tianhong , Anshuman Khandual , Matthew Wilcox , Alexey Klimov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] vmap(): don't allow invalid pages Message-ID: References: <20220118235244.540103-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220118235244.540103-1-yury.norov@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I replied ot the original RFC before spotting this; duplicating those comments here because I think they apply regardless of the mechanism used to work around this. On Tue, Jan 18, 2022 at 03:52:44PM -0800, Yury Norov wrote: > vmap() takes struct page *pages as one of arguments, and user may provide > an invalid pointer which would lead to DABT at address translation later. > > Currently, kernel checks the pages against NULL. In my case, however, the > address was not NULL, and was big enough so that the hardware generated > Address Size Abort on arm64. Can you give an example of when this might happen? It sounds like you're actually hitting this, so a backtrace would be nice. I'm a bit confused as to when why we'd try to vmap() pages that we didn't have a legitimate struct page for -- where did these addresses come from? It sounds like this is going wrong at a higher level, and we're passing entirely bogus struct page pointers around. This seems like the sort of thing DEBUG_VIRTUAL or similar should check when we initially generate the struct page pointer. > Interestingly, this abort happens even if copy_from_kernel_nofault() is > used, which is quite inconvenient for debugging purposes. I can go take a look at this, but TBH we never expect to take an address size fault to begin with, so this is arguably correct -- it's an internal consistency problem. > This patch adds a pfn_valid() check into vmap() path, so that invalid > mapping will not be created. > > RFC: https://lkml.org/lkml/2022/1/18/815 > v1: use pfn_valid() instead of adding an arch-specific > arch_vmap_page_valid(). Thanks to Matthew Wilcox for the hint. > > Signed-off-by: Yury Norov > --- > mm/vmalloc.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index d2a00ad4e1dd..a4134ee56b10 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -477,6 +477,8 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr, > return -EBUSY; > if (WARN_ON(!page)) > return -ENOMEM; > + if (WARN_ON(!pfn_valid(page_to_pfn(page)))) > + return -EINVAL; My fear here is that for this to fire, we've already passed a bogus struct page pointer around the intermediate infrastructure, and any of that might try to use it in unsafe ways (in future even if we don't use it today). I think the fundamental issue here is that we generate a bogus struct page pointer at all, and knowing where that came from would help to fix that. Thanks, Mark. > set_pte_at(&init_mm, addr, pte, mk_pte(page, prot)); > (*nr)++; > } while (pte++, addr += PAGE_SIZE, addr != end); > -- > 2.30.2 >