Messages in this thread | | | From | Peter Newman <> | Date | Fri, 16 Dec 2022 11:26:44 +0100 | Subject | Re: [PATCH v5 1/1] x86/resctrl: Fix task CLOSID/RMID update race |
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Hi Reinette,
On Fri, Dec 16, 2022 at 12:52 AM Reinette Chatre <reinette.chatre@intel.com> wrote: > > For a fix a Fixes: tag is expected. It looks like the following > may be relevant: > Fixes: ae28d1aae48a ("x86/resctrl: Use an IPI instead of task_work_add() to update PQR_ASSOC MSR") > Fixes: 0efc89be9471 ("x86/intel_rdt: Update task closid immediately on CPU in rmdir and unmount")
Thanks for preparing these lines. I'll include them.
> > > Signed-off-by: Peter Newman <peternewman@google.com> > > Also, please do let the stable team know about this via: > Cc: stable@vger.kernel.org
I wasn't sure if this fix met the criteria for backporting to stable, because I found it by code inspection, so it doesn't meet the "bothers people" criterion.
However I can make a case that it's exploitable:
"In a memory bandwidth-metered compute host, malicious jobs could exploit this race to remain in a previous CLOSID or RMID in order to dodge a class-of-service downgrade imposed by an admin or steal bandwidth."
> > Thank you very much for sticking with this and always paying attention > to the details along the way. > > Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Thank you, Reinette! This has been a learning experience for me.
-Peter
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