linux-kernel - Re: [PATCH 0/3] SG_IO command filtering via sysfs

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Message-ID: <20181116094810.GA23053@infradead.org>
Date:   Fri, 16 Nov 2018 01:48:10 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "Theodore Y. Ts'o" <tytso@....edu>, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, Hannes Reinecke <hare@...e.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>
Subject: Re: [PATCH 0/3] SG_IO command filtering via sysfs

On Fri, Nov 16, 2018 at 10:45:11AM +0100, Paolo Bonzini wrote:
> Yeah, but looking at the command is what Ted wants.  The thing that we
> did in RHEL was a single sysfs bool that allows unfiltered access,
> because it was sort of enough and made the delta very small.  But for
> upstream I want to do it right, even if that means learning all that
> new-fangled BPF stuff. :)

So what is this magic command?

> I would even agree, however it's allowed right now and I would be
> surprised if no one was relying on it in good faith ("I'm just doing an
> INQUIRY, why do I need to open O_RDWR").  And indeed:
> 
> $ sudo chmod a+r /dev/sda
> $ strace -e openat sg_inq /dev/sda
> openat(AT_FDCWD, "/dev/sda", O_RDONLY|O_NONBLOCK) = 3

Well, not if we only did that for unprivileged opens.