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

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Message-ID: <20181116093225.GA17033@infradead.org>
Date:   Fri, 16 Nov 2018 01:32:25 -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 Mon, Nov 12, 2018 at 11:17:29AM +0100, Paolo Bonzini wrote:
> > Well, that's what we have the security_file_ioctl() LSM hook for so that
> > your security model can arbitrate access to ioctls.
> 
> Doesn't that have TOC-TOU races by design?

If you want to look at the command - yes.  If you just want to filter
read vs write vs ioctl, no.

> Also, what about SG_IO giving write access to files that are only opened
> read-only (and only have read permissions)?

Allowing SG_IO on read-only permissions sounds like a reall bad idea,
filtering or not.