linux-kernel - [tip:x86/urgent] x86/video: Don't assume all FB devices are PCI devices

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Date:	Tue, 15 Mar 2016 03:39:40 -0700
From:	tip-bot for Vitaly Kuznetsov <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, bhelgaas@...gle.com, linux-kernel@...r.kernel.org,
	cavery@...hat.com, kys@...rosoft.com, helgaas@...nel.org,
	mingo@...nel.org, tglx@...utronix.de, vkuznets@...hat.com,
	torvalds@...ux-foundation.org, peterz@...radead.org
Subject: [tip:x86/urgent] x86/video: Don't assume all FB devices are PCI
 devices

Commit-ID:  743146db071c4a828159211a295d12ff4f61752f
Gitweb:     http://git.kernel.org/tip/743146db071c4a828159211a295d12ff4f61752f
Author:     Vitaly Kuznetsov <vkuznets@...hat.com>
AuthorDate: Tue, 15 Mar 2016 09:20:33 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 15 Mar 2016 11:08:26 +0100

x86/video: Don't assume all FB devices are PCI devices

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
  ...
   [<ffffffff81581308>] dump_stack+0x63/0x8b
   [<ffffffff812e1f99>] print_trailer+0xf9/0x150
   [<ffffffff812e7344>] object_err+0x34/0x40
   [<ffffffff812e9630>] kasan_report_error+0x230/0x550
   [<ffffffff812e9ee8>] kasan_report+0x58/0x60
   [<ffffffff812e4500>] ? ___slab_alloc+0x80/0x490
   [<ffffffff81878a28>] ? fb_is_primary_device+0x58/0x70
   [<ffffffff812e87cd>] __asan_load8+0x5d/0x70
   [<ffffffff81878a28>] fb_is_primary_device+0x58/0x70
   [<ffffffff8162357a>] register_framebuffer+0xda/0x5b0
   [<ffffffff816234a0>] ? 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.

While on it, clean up the function.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Bjorn Helgaas <helgaas@...nel.org>
Cc: Cathy Avery <cavery@...hat.com>
Cc: K. Y. Srinivasan <kys@...rosoft.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1458030033-10122-1-git-send-email-vkuznets@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/video/fbdev.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/arch/x86/video/fbdev.c b/arch/x86/video/fbdev.c
index d5644bb..9fd2484 100644
--- a/arch/x86/video/fbdev.c
+++ b/arch/x86/video/fbdev.c
@@ -14,26 +14,24 @@
 int fb_is_primary_device(struct fb_info *info)
 {
 	struct device *device = info->device;
-	struct pci_dev *pci_dev = NULL;
 	struct pci_dev *default_device = vga_default_device();
-	struct resource *res = NULL;
+	struct pci_dev *pci_dev;
+	struct resource *res;
 
-	if (device)
-		pci_dev = to_pci_dev(device);
-
-	if (!pci_dev)
+	if (!device || !dev_is_pci(device))
 		return 0;
 
+	pci_dev = to_pci_dev(device);
+
 	if (default_device) {
 		if (pci_dev == default_device)
 			return 1;
-		else
-			return 0;
+		return 0;
 	}
 
-	res = &pci_dev->resource[PCI_ROM_RESOURCE];
+	res = pci_dev->resource + PCI_ROM_RESOURCE;
 
-	if (res && res->flags & IORESOURCE_ROM_SHADOW)
+	if (res->flags & IORESOURCE_ROM_SHADOW)
 		return 1;
 
 	return 0;