Message-ID: <1544458624.18488.2.camel@redhat.com>
Subject: Re: [PATCH] block: Restore tape support
From: Laurence Oberman <loberman@redhat.com>
To: Jens Axboe <axboe@kernel.dk>, Keith Busch <keith.busch@intel.com>,
        Bart Van Assche <bvanassche@acm.org>
Cc: linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Todd Aiken <taiken@mvtech.ca>, stable@vger.kernel.org
Date: Mon, 10 Dec 2018 11:17:04 -0500
In-Reply-To: <93112026-a6b3-6db4-0c74-afbbbf6ca493@kernel.dk>
References: <20181210030814.13235-1-bvanassche@acm.org>
         <20181210153230.GB25206@localhost.localdomain>
         <93112026-a6b3-6db4-0c74-afbbbf6ca493@kernel.dk>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: stable-owner@vger.kernel.org

On Mon, 2018-12-10 at 08:36 -0700, Jens Axboe wrote:
> On 12/10/18 8:32 AM, Keith Busch wrote:
> > On Sun, Dec 09, 2018 at 07:08:14PM -0800, Bart Van Assche wrote:
> > > According to what I found in
> > > https://bugzilla.kernel.org/show_bug.cgi?id=201935 patch "block:
> > > Clear
> > > kernel memory before copying to user" broke tape access. Hence
> > > revert
> > > that patch.
> > 
> > Instead of reverting back to the leaking arbitrary kernel memory,
> > why
> > not just make a fix on top of it? This should do it:
> > 
> > ---
> > diff --git a/block/bio.c b/block/bio.c
> > index c4ef8aa46452..55a5386fd431 100644
> > --- a/block/bio.c
> > +++ b/block/bio.c
> > @@ -1262,7 +1262,8 @@ struct bio *bio_copy_user_iov(struct
> > request_queue *q,
> >  		if (ret)
> >  			goto cleanup;
> >  	} else {
> > -		zero_fill_bio(bio);
> > +		if (bmd->is_our_pages)
> > +			zero_fill_bio(bio);
> >  		iov_iter_advance(iter, bio->bi_iter.bi_size);
> >  	}
> >  
> 
> That should be fine, the other case is user mapped memory anyway.
> 

OK, I will test this today
Thanks folks!!
Laurence