linux-kernel - Re: [PATCH] block: don't set GD_NEED_PART

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZBrnxrQ8csN/xkRG@ovpn-8-17.pek2.redhat.com>
Date:   Wed, 22 Mar 2023 19:34:30 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Yu Kuai <yukuai1@...weicloud.com>, hch@...radead.org,
        axboe@...nel.dk, yukuai3@...wei.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, ming.lei@...hat.com,
        Xiao Ni <xni@...hat.com>, linux-raid@...r.kernel.org
Subject: Re: [PATCH] block: don't set GD_NEED_PART_SCAN if scan partition
 failed

On Wed, Mar 22, 2023 at 10:47:07AM +0100, Jan Kara wrote:
> On Wed 22-03-23 15:58:35, Ming Lei wrote:
> > On Wed, Mar 22, 2023 at 11:59:26AM +0800, Yu Kuai wrote:
> > > From: Yu Kuai <yukuai3@...wei.com>
> > > 
> > > Currently if disk_scan_partitions() failed, GD_NEED_PART_SCAN will still
> > > set, and partition scan will be proceed again when blkdev_get_by_dev()
> > > is called. However, this will cause a problem that re-assemble partitioned
> > > raid device will creat partition for underlying disk.
> > > 
> > > Test procedure:
> > > 
> > > mdadm -CR /dev/md0 -l 1 -n 2 /dev/sda /dev/sdb -e 1.0
> > > sgdisk -n 0:0:+100MiB /dev/md0
> > > blockdev --rereadpt /dev/sda
> > > blockdev --rereadpt /dev/sdb
> > > mdadm -S /dev/md0
> > > mdadm -A /dev/md0 /dev/sda /dev/sdb
> > > 
> > > Test result: underlying disk partition and raid partition can be
> > > observed at the same time
> > > 
> > > Note that this can still happen in come corner cases that
> > > GD_NEED_PART_SCAN can be set for underlying disk while re-assemble raid
> > > device.
> > > 
> > > Fixes: e5cfefa97bcc ("block: fix scan partition for exclusively open device again")
> > > Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> > 
> > The issue still can't be avoided completely, such as, after rebooting,
> > /dev/sda1 & /dev/md0p1 can be observed at the same time. And this one
> > should be underlying partitions scanned before re-assembling raid, I
> > guess it may not be easy to avoid.
> 
> So this was always happening (before my patches, after my patches, and now
> after Yu's patches) and kernel does not have enough information to know
> that sda will become part of md0 device in the future. But mdadm actually
> deals with this as far as I remember and deletes partitions for all devices
> it is assembling the array from (and quick tracing experiment I did
> supports this).

I am testing on Fedora 37, so mdadm v4.2 doesn't delete underlying
partitions before re-assemble.

Also given mdadm or related userspace has to change for avoiding
to scan underlying partitions, just wondering why not let userspace
to tell kernel not do it explicitly?

Thanks,
Ming