linux-kernel - Re: [PATCH] sg, bsg: mitigate read/write abuse, block uaccess in release

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Message-ID: <229a6637-3f9e-e8ed-d94a-cafbbd47f140@kernel.dk>
Date:   Mon, 18 Jun 2018 10:23:45 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     dgilbert@...erlog.com, Jann Horn <jannh@...gle.com>,
        FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
        "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-block@...r.kernel.org, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        security@...nel.org
Subject: Re: [PATCH] sg, bsg: mitigate read/write abuse, block uaccess in
 release

On 6/18/18 10:16 AM, Al Viro wrote:
> On Mon, Jun 18, 2018 at 09:37:01AM -0600, Jens Axboe wrote:
> 
>>> The folks responsible are no longer active in kernel development ***
>>> but as far as I know the async write(command), read(response) were
>>> added to bsg over 10 years ago as proof-of-concept and never properly
>>> worked in this async mode. The biggest design problem with it that I'm
>>
>> It was born with that mode, but I don't think anyone ever really used it.
>> So it might feasible to simply yank it. That said, just doing a prune
>> mode at ->release() time doesn't seem like such a hard task.
> 
> "prune mode" being...?

Basically what Jann posted, not doing any copy-back of data. Need to
verify if the bio unmapping is handled correctly, as some of those
will also copy when the end_io handling is invoked.

-- 
Jens Axboe