linux-kernel - Re: usercopy whitelist woe in scsi_sense

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Message-ID: <d31189fc94392eb733c1e310ac1ec498@natalenko.name>
Date:   Tue, 10 Apr 2018 15:47:41 +0200
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     Kees Cook <keescook@...omium.org>
Cc:     David Windsor <dave@...lcore.net>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Hannes Reinecke <hare@...e.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        linux-block@...r.kernel.org, paolo.valente@...aro.org,
        keescook@...gle.com
Subject: Re: usercopy whitelist woe in scsi_sense_cache

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@...hlinux ~]# 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