Re: [PATCH 0/9 v7] bfq: Avoid use-after-free when moving processes between cgroups

Paolo Valente
2022-04-26T14:29:38Z

> Il giorno 1 apr 2022, alle ore 12:27, Jan Kara <jack@suse.cz> ha scritto:
>
> Hello,
>
> here is the seventh version of my patches to fix use-after-free issues in BFQ
> when processes with merged queues get moved to different cgroups. Kuai has
> confirmed that patches now fix all the issues his reproducer was able to
> trigger so I've just added some tags, codewise this is the same as v6. Paolo,
> can you please check whether the patches look good to you so that Jens can
> merge them?

I think this is not needed any longer :) At any rate, your patches do fix
an evident problem, in a correct way.

Thank you,
Paolo

> Thanks!
>
> Changes since v6:
> * Added some Tested-by, Fixes, and CC tags
>
> Changes since v5:
> * Added handling of situation when bio is submitted for a cgroup that has
> already went through bfq_pd_offline()
> * Convert bfq to avoid using deprecated __bio_blkcg() and thus fix possible
> races when returned cgroup can change while bfq is working with a request
>
> Changes since v4:
> * Even more aggressive splitting of merged bfq queues to avoid problems with
> long merge chains.
>
> Changes since v3:
> * Changed handling of bfq group move to handle the case when target of the
> merge has moved.
>
> Changes since v2:
> * Improved handling of bfq queue splitting on move between cgroups
> * Removed broken change to bfq_put_cooperator()
>
> Changes since v1:
> * Added fix for bfq_put_cooperator()
> * Added fix to handle move between cgroups in bfq_merge_bio()
>
> Honza
> Previous versions:
> Link: http://lore.kernel.org/r/20211223171425.3551-1-jack@suse.cz # v1
> Link: http://lore.kernel.org/r/20220105143037.20542-1-jack@suse.cz # v2
> Link: http://lore.kernel.org/r/20220112113529.6355-1-jack@suse.cz # v3
> Link: http://lore.kernel.org/r/20220114164215.28972-1-jack@suse.cz # v4
> Link: http://lore.kernel.org/r/20220121105503.14069-1-jack@suse.cz # v5
> Link: http://lore.kernel.org/r/20220330123438.32719-1-jack@suse.cz # v6