From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753372AbcCLU6a (ORCPT ); Sat, 12 Mar 2016 15:58:30 -0500 Received: from mail.kernel.org ([198.145.29.136]:40627 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752666AbcCLU63 (ORCPT ); Sat, 12 Mar 2016 15:58:29 -0500 Date: Sat, 12 Mar 2016 14:58:24 -0600 From: Bjorn Helgaas To: Vitaly Kuznetsov Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Cathy Avery , "K. Y. Srinivasan" Subject: Re: [PATCH] x86: don't assume all fb devices are PCI devices Message-ID: <20160312205824.GA26840@localhost> References: <1457707158-11202-1-git-send-email-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1457707158-11202-1-git-send-email-vkuznets@redhat.com> 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 On Fri, Mar 11, 2016 at 03:39:18PM +0100, Vitaly Kuznetsov wrote: > When booting Hyper-V Generation 2 guests KASAN reports the following > out-of-bounds access: > > BUG: KASAN: slab-out-of-bounds in fb_is_primary_device+0x58/0x70 at addr > ffff880079cf0eb0 > Read of size 8 by task swapper/0/1 > ... > [] dump_stack+0x63/0x8b > [] print_trailer+0xf9/0x150 > [] object_err+0x34/0x40 > [] kasan_report_error+0x230/0x550 > [] kasan_report+0x58/0x60 > [] ? ___slab_alloc+0x80/0x490 > [] ? fb_is_primary_device+0x58/0x70 > [] __asan_load8+0x5d/0x70 > [] fb_is_primary_device+0x58/0x70 > [] register_framebuffer+0xda/0x5b0 > [] ? remove_conflicting_framebuffers+0x50/0x50 > ... > > The issue is caused by the to_pci_dev() call with no check that the given > info->device is in fact a pci device and some fb devices (Hyper-V FB, EFI > FB,...) are not. fb_is_primary_device() is not on any performance critical > path, replace to_pci_dev() with raw scan. > > Signed-off-by: Vitaly Kuznetsov > --- > arch/x86/video/fbdev.c | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/video/fbdev.c b/arch/x86/video/fbdev.c > index d5644bb..f309d6c 100644 > --- a/arch/x86/video/fbdev.c > +++ b/arch/x86/video/fbdev.c > @@ -14,12 +14,18 @@ > int fb_is_primary_device(struct fb_info *info) > { > struct device *device = info->device; > - struct pci_dev *pci_dev = NULL; > + struct pci_dev *dev = NULL, *pci_dev = NULL; > struct pci_dev *default_device = vga_default_device(); > struct resource *res = NULL; > > - if (device) > - pci_dev = to_pci_dev(device); > + /* > + * We're not sure info->device is a pci device, do full scan instead > + * of to_pci_dev(). > + */ > + for_each_pci_dev(dev) { > + if (&dev->dev == device) > + pci_dev = dev; > + } > if (!pci_dev) > return 0; I think dev_is_pci() is a better solution: if (!device || !dev_is_pci(device)) return 0; pci_dev = to_pci_dev(device); if (vga_default_device()) { if (vga_default_device() == pci_dev) return 1; return 0; } res = &pci_dev->resource[PCI_ROM_RESOURCE]; if (res->flags & IORESOURCE_ROM_SHADOW) return 1; return 0; This says a non-PCI device cannot be the primary device. I don't know framebuffers, so I don't know if that's what you really want, but I guess it's what the original code says. Bjorn