Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754937AbbKJSGU (ORCPT ); Tue, 10 Nov 2015 13:06:20 -0500 Received: from 8bytes.org ([81.169.241.247]:38171 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753864AbbKJR5d (ORCPT ); Tue, 10 Nov 2015 12:57:33 -0500 Date: Tue, 10 Nov 2015 18:57:32 +0100 From: Joerg Roedel To: Linus Torvalds Cc: "open list:AMD IOMMU (AMD-VI)" , Oded Gabbay , David Woodhouse , Linux Kernel Mailing List , Joerg Roedel Subject: Re: [PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm_fault() Message-ID: <20151110175731.GC13027@8bytes.org> References: <1447162006-20672-1-git-send-email-joro@8bytes.org> <1447162006-20672-5-git-send-email-joro@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1471 Lines: 45 On Tue, Nov 10, 2015 at 09:43:03AM -0800, Linus Torvalds wrote: > On Tue, Nov 10, 2015 at 5:26 AM, Joerg Roedel wrote: > > + > > +static bool access_error(struct vm_area_struct *vma, struct page_req_dsc *req) > > +{ > > + return !((req->rd_req && (vma->vm_flags & VM_READ)) || > > + (req->wr_req && (vma->vm_flags & VM_WRITE)) || > > + (req->exe_req && (vma->vm_flags & VM_EXEC))); > > +} > > This seems odd. > > Shouldn't it be > > return ((req->rd_req && !(vma->vm_flags & VM_READ)) || > (req->wr_req && !(vma->vm_flags & VM_WRITE)) || > (req->exe_req && !(vma->vm_flags & VM_EXEC))); > > instead? Yes, thats better, it solves the multiple-bits-set problem too, which David mentioned. > Of course, if you just used the VM_xyz flags internally itself, this > would all be easier, and you'd end up with something like > > /* Do we have requested bits that aren't in the allowed set? */ > return (requested & ~vma->vm_flags) != 0; > > instead.. But this is probably the best solution, some architecture page-fault handlers do something similar. I'll update the patch and use this for the AMD part too. Thanks, Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/