linux-kernel - Re: [PATCH] PCI: Fix pcibios_update

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 03 Feb 2015 11:37:30 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Andre Przywara <Andre.Przywara@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH] PCI: Fix pcibios_update_irq misuse of irq number

On 03/02/15 11:31, Arnd Bergmann wrote:
> On Tuesday 03 February 2015 10:38:25 Marc Zyngier wrote:
>>
>> That's exactly what I thought until Lorenzo reported kvmtool falling
>> over because of this write. Obviously, some platforms must actually
>> require this (possibly for bridges that are not known by the firmware).
> 
> This sounds much like a bug in kvmtool.

Lorenzo and I just came to a similar conclusion, given that the HW
should never use that information.

>> Entirely removing that code solves my problem too, but that'd cannot be
>> the right solution...
> 
> The comment in pdev_fixup_irq() says 
> 
>         /* Always tell the device, so the driver knows what is
>            the real IRQ to use; the device does not use it. */
> 
> which I read to mean that there are drivers that incorrectly use
> 'pci_read_config_byte(dev, PCI_INTERRUPT_LINE)' as the number
> they pass into request_irq, rather than using dev->irq.
> However, this means that your patch is actually wrong, because
> what the driver cares about is the virtual irq number (which
> request_irq expects), not the number relative to some interrupt
> controller.

Yes, I now realise that. That makes a lot more sense actually, because I
was getting very confused about how the HW should interpret that number.

Side question: In the probe-only case, should we still allow this write
to happen?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/