From: Igor Mammedov <imammedo@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: acpi_pcihp_eject_slot() bug if passed 'slots == 0'
Date: Thu, 26 Mar 2020 14:23:17 +0100 [thread overview]
Message-ID: <20200326142317.018c13e1@redhat.com> (raw)
In-Reply-To: <CAFEAcA-oWBjOXWmnLvPww9wrty_QbSc+Xv3BY3sQAnEXFkfQbA@mail.gmail.com>
On Thu, 26 Mar 2020 11:52:36 +0000
Peter Maydell <peter.maydell@linaro.org> wrote:
> Hi; Coverity spots that if hw/acpi/pcihp.c:acpi_pcihp_eject_slot()
> is passed a zero 'slots' argument then ctz32(slots) will return 32,
> and then the code that does '1U << slot' is C undefined behaviour
> because it's an oversized shift. (This is CID 1421896.)
>
> Since the pci_write() function in this file can call
> acpi_pcihp_eject_slot() with an arbitrary value from the guest,
> I think we need to handle 'slots == 0' safely. But what should
> the behaviour be?
it also uncovers a bug, where we are not able to eject slot 0 on bridge,
can be reproduced with:
-enable-kvm -m 4G -device pci-bridge,chassis_nr=1 -global PIIX4_PM.acpi-pci-hotplug-with-bridge-support=on -device virtio-net-pci,bus=pci.1,addr=0,id=netdev12
(monitor) device_del netdev12
(monitor) qtree # still shows the device
reason is that acpi_pcihp_eject_slot()
if (PCI_SLOT(dev->devfn) == slot) { # doesn't match (0 != 32)
so device is not deleted
> thanks
> -- PMM
>
next prev parent reply other threads:[~2020-03-26 13:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-26 11:52 acpi_pcihp_eject_slot() bug if passed 'slots == 0' Peter Maydell
2020-03-26 12:29 ` Igor Mammedov
2020-03-26 12:50 ` Igor Mammedov
2020-03-26 13:29 ` Michael S. Tsirkin
2020-03-26 13:23 ` Igor Mammedov [this message]
2020-03-26 13:28 ` Michael S. Tsirkin
2020-03-26 13:31 ` Michael S. Tsirkin
2020-03-26 13:40 ` Igor Mammedov
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