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Date: Tue, 10 Apr 2018 15:47:41 +0200
From: Oleksandr Natalenko <oleksandr@natalenko.name>
To: Kees Cook <keescook@chromium.org>
Cc: David Windsor <dave@nullcore.net>,
        "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
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        Hannes Reinecke <hare@suse.com>,
        Johannes Thumshirn <jthumshirn@suse.de>, linux-block@vger.kernel.org,
        paolo.valente@linaro.org, keescook@google.com
Subject: Re: usercopy whitelist woe in scsi_sense_cache
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Hi.

10.04.2018 08:35, Oleksandr Natalenko wrote:
>> - does it reproduce _without_ hardened usercopy? (I would assume yes,
>> but you'd just not get any warning until the hangs started.) If it
>> does reproduce without hardened usercopy, then a new bisect run could
>> narrow the search even more.
> 
> Looks like it cannot be disabled via kernel cmdline, so I have to
> re-compile the kernel, right? I can certainly do that anyway.

Okay, I've recompiled the kernel without hardened usercopy:

[root@archlinux ~]# zgrep USERCOPY /proc/config.gz
CONFIG_X86_INTEL_USERCOPY=y
CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR=y
# CONFIG_HARDENED_USERCOPY is not set

and I cannot reproduce the issue anymore. I/O doesn't hang regardless of 
how long I hammer it.

Eeeh? Maybe, this is a matter of some cleanup code path once the 
warn/bug condition is hit with hardening enabled? I'm just guessing here 
again.

Will work towards checking Linus' master branch now…

Regards,
   Oleksandr