From: Eric Sandeen <sandeen@redhat.com>
To: Martin Wilck <martin.wilck@ts.fujitsu.com>
Cc: linux-ext4@vger.kernel.org
Subject: Re: GRUB and the risk of block list corruption in extX
Date: Thu, 07 Feb 2013 09:50:07 -0600 [thread overview]
Message-ID: <5113CD2F.9010908@redhat.com> (raw)
In-Reply-To: <51137F76.8070705@ts.fujitsu.com>
On 2/7/13 4:18 AM, Martin Wilck wrote:
> Hello,
>
> you may have seen the following warning that is displayed when
> someone tries to install GRUB2 on in a extX partition:
>
> "/sbin/grub-setup: warn: Embedding is not possible. GRUB can only be
> installed in this setup by using blocklists. However, blocklists are
> UNRELIABLE and their use is discouraged."
To be clear, this is only the case when installing the bootloader itself to
a partition containing a filesystem, not when installing to the MBR, correct?
Which is different than saying "/boot is on ext4" - it's putting the bootloader
itself on a partition containing a filesystem, something which is a bit more
unusual, I think.
-Eric
> Recently I have been involved in discussions about this on
> https://bugzilla.redhat.com/show_bug.cgi?id=872826.
>
> The Grub manual says "installing to a filesystem means that GRUB is
> vulnerable to its blocks being moved around by filesystem features such
> as tail packing, or even by aggressive fsck implementations".
>
> My question to the extX experts: Under what circumstances (except
> modifying, overwriting, deleting the bootloader image "core.img" itself)
> can a block list referencing "core.img" be corrupted? In particular:
>
> 1) could it happen during ordinary operation, filesystem code silently
> moving blocks around?
> 2) could it happen in an e2fsck run?
> 3) could it be caused by e4defrag?
> 4) could it happen with resize2fs even if the blocks occupied by the
> file fit in the size that the FS is resized to (otherwise obviously "yes")?
> 5) Anything else?
> 6) if the file was protected with the IMMUTABLE flag, would any of 1-5
> still be able to corrupt the file?
>
> Regards
> Martin
>
next prev parent reply other threads:[~2013-02-07 15:50 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-07 10:18 GRUB and the risk of block list corruption in extX Martin Wilck
2013-02-07 13:27 ` Jan Kara
2013-02-07 15:50 ` Eric Sandeen [this message]
2013-02-07 20:53 ` Theodore Ts'o
2013-02-08 10:15 ` Martin Wilck
-- strict thread matches above, loose matches on Subject: below --
2013-02-10 0:17 Chris Murphy
2013-02-10 4:45 ` Theodore Ts'o
2013-02-11 15:38 ` Eric Sandeen
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