Re: [PATCH V6 1/2] nvme: enable char device per namespace

From: "hch@lst.de" <hch@lst.de>
To: Minwoo Im <minwoo.im.dev@gmail.com>
Cc: "Niklas Cassel" <Niklas.Cassel@wdc.com>,
	"javier@javigon.com" <javier@javigon.com>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"sagi@grimberg.me" <sagi@grimberg.me>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"kbusch@kernel.org" <kbusch@kernel.org>,
	"Javier González" <javier.gonz@samsung.com>,
	"hch@lst.de" <hch@lst.de>
Subject: Re: [PATCH V6 1/2] nvme: enable char device per namespace
Date: Thu, 25 Mar 2021 09:26:47 +0100	[thread overview]
Message-ID: <20210325082647.GA27622@lst.de> (raw)
In-Reply-To: <20210325020951.GA2105@localhost>

On Thu, Mar 25, 2021 at 11:09:51AM +0900, Minwoo Im wrote:
> > I was still allowed to write to NSID2:
> > 
> > sudo nvme zns report-zones -d 1 /dev/nvme0n2
> > SLBA: 0x0        WP: 0x1        Cap: 0x3e000    State: IMP_OPENED   Type: SEQWRITE_REQ   Attrs: 0x0
> > 
> > Should this really be allowed?
> 
> I think this should not be allowed at all.  Thanks for the testing!

It should not be allowed, but it seems like a pre-existing problem
as nvme_user_cmd does not verify the nsid.

> > I was under the impression that Christoph's argument for implementing per
> > namespace char devices, was that you should be able to do access control.
> > Doesn't that mean that for the new char devices, we need to reject ioctls
> > that specify a nvme_passthru_cmd.nsid != the NSID that the char device
> > represents?
> > 
> > 
> > Although, this is not really something new, as we already have the same
> > behavior when it comes ioctls and the block devices. Perhaps we want to
> > add the same verification there?
> 
> I think there should be verifications.

Yes.

> > Regardless if we want to add a verification for block devices or not,
> > it just seemed to me that the whole argument for introducing new char
> > devices was to allow access control per namespace, which doesn't seem
> > to have been taken into account, but perhaps I'm missing something.
> 
> Any other points that you think it's not been taken account?  I think it
> should map to previous blkdev operations, but with some verfications
> there.  It would be great if you can share any other points supposed to
> be supported here :)

Agreed.

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