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SubjectRe: usercopy whitelist woe in scsi_sense_cache
On Sun, Apr 8, 2018 at 12:07 PM, Oleksandr Natalenko
<> 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:


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]
> [2]

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


Kees Cook
Pixel Security

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