From: Paolo Bonzini <pbonzini@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>,
linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
Hannes Reinecke <hare@suse.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
James Bottomley <James.Bottomley@hansenpartnership.com>
Subject: Re: [PATCH 0/3] SG_IO command filtering via sysfs
Date: Fri, 16 Nov 2018 10:45:11 +0100 [thread overview]
Message-ID: <fa3ed175-13a3-bedf-ebf9-ddf46a2decd5@redhat.com> (raw)
In-Reply-To: <20181116093225.GA17033@infradead.org>
On 16/11/18 10:32, Christoph Hellwig wrote:
> 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.
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. :)
>> 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.
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
^^^^^^^^
So it would be a regression.
Paolo
next prev parent reply other threads:[~2018-11-16 9:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-10 16:35 [PATCH 0/3] SG_IO command filtering via sysfs Paolo Bonzini
2018-11-10 16:35 ` [PATCH 1/3] block: add back queue-private command filter Paolo Bonzini
2018-11-10 16:35 ` [PATCH 2/3] scsi: create an all-one filter for scanners Paolo Bonzini
2018-11-10 16:35 ` [PATCH 3/3] block: add back command filter modification via sysfs Paolo Bonzini
2018-11-16 5:46 ` Bart Van Assche
2018-11-16 7:00 ` Paolo Bonzini
2018-11-16 14:42 ` Bart Van Assche
2018-11-10 19:05 ` [PATCH 0/3] SG_IO command filtering " Theodore Y. Ts'o
2018-11-11 13:26 ` Paolo Bonzini
2018-11-11 14:14 ` Theodore Y. Ts'o
2018-11-16 0:26 ` Paolo Bonzini
2018-11-16 0:37 ` Bart Van Assche
2018-11-16 7:01 ` Paolo Bonzini
2018-11-16 17:35 ` Theodore Y. Ts'o
2018-11-11 13:14 ` Christoph Hellwig
2018-11-11 13:42 ` Theodore Y. Ts'o
2018-11-12 8:20 ` Christoph Hellwig
2018-11-12 10:17 ` Paolo Bonzini
2018-11-16 9:32 ` Christoph Hellwig
2018-11-16 9:45 ` Paolo Bonzini [this message]
2018-11-16 9:48 ` Christoph Hellwig
2018-11-16 17:43 ` Theodore Y. Ts'o
2018-11-16 18:17 ` Bart Van Assche
2018-11-16 21:08 ` Paolo Bonzini
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