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    SubjectRe: usercopy whitelist woe in scsi_sense_cache
    On Sun, Apr 8, 2018 at 12:07 PM, Oleksandr Natalenko
    <oleksandr@natalenko.name> wrote:
    > So far, I wasn't able to trigger this with mq-deadline (or without blk-mq).
    > Maybe, this has something to do with blk-mq+BFQ re-queuing, or it's just me
    > not being persistent enough.

    Ah, this detail I didn't have. I've changed my environment to

    build with:

    CONFIG_BLK_MQ_PCI=y
    CONFIG_BLK_MQ_VIRTIO=y
    CONFIG_IOSCHED_BFQ=y

    boot with scsi_mod.use_blk_mq=1

    and select BFQ in the scheduler:

    # cat /sys/block/sd?/queue/scheduler
    mq-deadline kyber [bfq] none
    mq-deadline kyber [bfq] none

    Even with this, I'm not seeing anything yet...

    > It looks like this code path was re-written completely with 17cb960f29c2, but
    > it went merged for the upcoming v4.17 only, and thus I haven't tried it yet.
    >
    > Kees took a brief look at it already: [1]. This is what smartctl does [2]
    > (just a usual strace capture when the bug is not triggered).
    >
    > Christoph, do you have some idea on why this can happen?
    >
    > Thanks.
    >
    > Regards,
    > Oleksandr
    >
    > [1] https://marc.info/?l=linux-scsi&m=152287333013845&w=2
    > [2] https://gist.github.com/pfactum/6f58f8891468aeba1ab2cc9f45668735

    The thing I can't figure out is how req->sense is slipping forward in
    (and even beyond!) the allocation.

    -Kees

    --
    Kees Cook
    Pixel Security

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