Messages in this thread | | | Date | Sat, 11 Dec 2021 00:12:35 +0100 | From | Michal Koutný <> | Subject | Re: [PATCH] exit: Retain nsproxy for exit_task_work() work entries |
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On Wed, Dec 08, 2021 at 12:45:54PM -0600, "Eric W. Biederman" <ebiederm@xmission.com> wrote: > TL;DR the cgroup file system is checking permissions at write time.
Thank you for bringing that up (handled in a separate thread now).
> I think I follow your reasoning and I think it will even fix the issue > but no.
FTR, part of Tejun's series [1] ensures that cgroup_ns is accessed directly without nsproxy and a reference to it is kept while the file is opened. I.e. that'd properly fix this particular crash reported by syzbot.
> Please don't apply this patch. > > exit_task_work running after exit_task_namespaces is the messenger > that just told us about something ugly.
In (my) theory some other task_work callbacks could (transitively) rely on the current->nsproxy which could still be cleared by exit_task_namespaces(). Is there another reason why to have exit_task_namespaces() before exit_task_work()?
Thanks, Michal
[1] https://lore.kernel.org/r/20211209214707.805617-4-tj@kernel.org/
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