Re: [PATCH v1] xen/sched/null: avoid crash after failed domU creation

[Juergen Gross <jgross@xxxxxxxx>]

On 01.05.23 22:30, Stewart Hildebrand wrote:
> When creating a domU, but the creation fails, there is a corner case that may
> lead to a crash in the null scheduler when running a debug build of Xen.
>
> (XEN) ****************************************
> (XEN) Panic on CPU 0:
> (XEN) Assertion 'npc->unit == unit' failed at common/sched/null.c:379
> (XEN) ****************************************
>
> The events leading to the crash are:
>
> * null_unit_insert() was invoked with the unit offline. Since the unit was
>    offline, unit_assign() was not called, and null_unit_insert() returned.
> * Later during domain creation, the unit was onlined
> * Eventually, domain creation failed due to bad configuration
> * null_unit_remove() was invoked with the unit still online. Since the unit was
>    online, it called unit_deassign() and triggered an ASSERT.
>
> To fix this, only call unit_deassign() when npc->unit is non-NULL in
> null_unit_remove.
>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

Attachment: OpenPGP_0xB0DE9DD628BF132F.asc
Description: OpenPGP public key

Attachment: OpenPGP_signature
Description: OpenPGP digital signature