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Re: [PATCH] IOMMU: make domctl handler tolerate NULL domain
- To: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 19 Apr 2022 12:59:00 +0200
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- Cc: Paul Durrant <paul@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 19 Apr 2022 10:59:05 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 19.04.2022 12:49, Andrew Cooper wrote:
> On 19/04/2022 10:39, Jan Beulich wrote:
>> Besides the reporter's issue of hitting a NULL deref when !CONFIG_GDBSX,
>> XEN_DOMCTL_test_assign_device can legitimately end up having NULL passed
>> here, when the domctl was passed DOMID_INVALID.
>>
>> Fixes: 71e617a6b8f6 ("use is_iommu_enabled() where appropriate...")
>> Reported-by: Cheyenne Wills <cheyenne.wills@xxxxxxxxx>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> I disagree with the Reported-by tag here. At best, it's "also noticed
> while investigating".
One can view that way as well, sure. But this change alone would be
sufficient to address the report. (As would be Jürgen's change alone.)
> Furthermore, under what circumstances is test_assign_device legitimate
> when passing DOMID_INVALID ? This has been broken for 3 years now
> without report, so it's clearly an unused codepath under both xl's and
> xapi's idea of passthrough.
I guess xend had a way to drive the domctl this way. Iirc this was
to find out whether a device is assignable at all, without needing
to know of any particular valid domain.
Jan
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