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 X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B44AEC433DF for ; Thu, 14 May 2020 11:14:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9001F206DA for ; Thu, 14 May 2020 11:14:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726140AbgENLOq (ORCPT ); Thu, 14 May 2020 07:14:46 -0400 Received: from verein.lst.de ([213.95.11.211]:51366 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725955AbgENLOq (ORCPT ); Thu, 14 May 2020 07:14:46 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 951B268BEB; Thu, 14 May 2020 13:14:42 +0200 (CEST) Date: Thu, 14 May 2020 13:14:42 +0200 From: Christoph Hellwig To: Jeremy Linton Cc: Christoph Hellwig , Greg KH , Hillf Danton , syzbot , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com, x86@kernel.org Subject: Re: Validating dma_mmap_coherent() parameters before calling (was Re: WARNING in memtype_reserve) Message-ID: <20200514111442.GA13813@lst.de> References: <000000000000f0d8d205a531f1a3@google.com> <20200509074507.GC1831917@kroah.com> <87wo5l4ecm.fsf@nanos.tec.linutronix.de> <20200513124445.GA1082735@kroah.com> <87zhab249p.fsf@nanos.tec.linutronix.de> <20200514035458.14760-1-hdanton@sina.com> <20200514061417.GA8367@lst.de> <20200514062750.GA1488715@kroah.com> <20200514063158.GA8780@lst.de> <8bdb3488-59d0-67ce-4822-e25dbd0dc42a@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8bdb3488-59d0-67ce-4822-e25dbd0dc42a@arm.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 14, 2020 at 06:10:03AM -0500, Jeremy Linton wrote: >> I only need to look at the commit for 3 seconds to tell you that it is >> completely buggy. While using dma_mmap_coherent is fundamentally the >> right thing and absolutely required for dma_alloc_* allocations, USB >> also uses it's own local gen pool allocator or plain kmalloc for not >> DMA capable controller. This need to use remap_pfn_range. I'm pretty >> sure you hit one of those cases. > > ? The code path in question is usbdev_mmap() and the allocation is done ~13 > lines lines before as a usb_alloc_coherent(). And did you take a look at how usb_alloc_coherent is implemented? That should make it completely obvious that not all allocations come from dma_alloc_*. > That sort of makes sense, except for the above, and the fact that I would > imagine the dma_mmap_coherent should be dealing with that case. I'm not > really clear about the details of the GCE usb device here, but my first > guess at this was the dma_pgprot() in dma_direct_mmap() is incorrectly > picking a pgprot... No, dma_mmap_* / dma_direct_mmap has absolutely no business dealing with memory that did not come from the DMA allocator.