From: Juergen Gross <jgross@suse.com>
To: Paul Durrant <paul@xen.org>,
xen-devel@lists.xenproject.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Paul Durrant <pdurrant@amazon.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH v3] xen-blkback: fix compatibility bug with single page rings
Date: Fri, 23 Apr 2021 10:04:00 +0200 [thread overview]
Message-ID: <1327bf3a-f5cf-6e1f-1a0e-e55aeabf787d@suse.com> (raw)
In-Reply-To: <20210202175659.18452-1-paul@xen.org>
[-- Attachment #1.1.1: Type: text/plain, Size: 1649 bytes --]
On 02.02.21 18:56, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@amazon.com>
>
> Prior to commit 4a8c31a1c6f5 ("xen/blkback: rework connect_ring() to avoid
> inconsistent xenstore 'ring-page-order' set by malicious blkfront"), the
> behaviour of xen-blkback when connecting to a frontend was:
>
> - read 'ring-page-order'
> - if not present then expect a single page ring specified by 'ring-ref'
> - else expect a ring specified by 'ring-refX' where X is between 0 and
> 1 << ring-page-order
>
> This was correct behaviour, but was broken by the afforementioned commit to
> become:
>
> - read 'ring-page-order'
> - if not present then expect a single page ring (i.e. ring-page-order = 0)
> - expect a ring specified by 'ring-refX' where X is between 0 and
> 1 << ring-page-order
> - if that didn't work then see if there's a single page ring specified by
> 'ring-ref'
>
> This incorrect behaviour works most of the time but fails when a frontend
> that sets 'ring-page-order' is unloaded and replaced by one that does not
> because, instead of reading 'ring-ref', xen-blkback will read the stale
> 'ring-ref0' left around by the previous frontend will try to map the wrong
> grant reference.
>
> This patch restores the original behaviour.
>
> Fixes: 4a8c31a1c6f5 ("xen/blkback: rework connect_ring() to avoid inconsistent xenstore 'ring-page-order' set by malicious blkfront")
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> Reviewed-by: Dongli Zhang <dongli.zhang@oracle.com>
> Reviewed-by: "Roger Pau Monné" <roger.pau@citrix.com>
Pushed to xen/tip.git for-linus-5.13
Juergen
[-- Attachment #1.1.2: OpenPGP_0xB0DE9DD628BF132F.asc --]
[-- Type: application/pgp-keys, Size: 3135 bytes --]
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 495 bytes --]
prev parent reply other threads:[~2021-04-23 8:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-02 17:56 [PATCH v3] xen-blkback: fix compatibility bug with single page rings Paul Durrant
2021-04-23 8:04 ` Juergen Gross [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1327bf3a-f5cf-6e1f-1a0e-e55aeabf787d@suse.com \
--to=jgross@suse.com \
--cc=axboe@kernel.dk \
--cc=konrad.wilk@oracle.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=paul@xen.org \
--cc=pdurrant@amazon.com \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).