lkml.org 
[lkml]   [2016]   [Mar]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] x86: don't assume all fb devices are PCI devices
On Mon, Mar 14, 2016 at 03:42:57PM +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
> ...
> [<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.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
> Changes since v1: use dev_is_pci() instead of full scan [Bjorn Helgaas].
> ---
> arch/x86/video/fbdev.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/video/fbdev.c b/arch/x86/video/fbdev.c
> index d5644bb..9f2fe63 100644
> --- a/arch/x86/video/fbdev.c
> +++ b/arch/x86/video/fbdev.c
> @@ -18,12 +18,11 @@ int fb_is_primary_device(struct fb_info *info)
> struct pci_dev *default_device = vga_default_device();
> struct resource *res = NULL;

The initializations of "pci_dev" and "res" to NULL are now
unnecessary.

>
> - 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;

The test for non-NULL "res" below is superfluous because we know
"pci_dev" is non-NULL:

res = &pci_dev->resource[PCI_ROM_RESOURCE];
if (res && res->flags & IORESOURCE_ROM_SHADOW)

I think your patch is functionally correct, so it's up to you and the
x86 guys whether you want to do these additional cleanups.

Bjorn

\
 
 \ /
  Last update: 2016-03-14 16:41    [W:0.037 / U:1.708 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site