From: Maurizio Lombardi <m.lombardi85@gmail.com>
To: dave@gnu.org
Cc: util-linux@vger.kernel.org
Subject: Re: mkfs.minix V3 is broken
Date: Tue, 22 Nov 2011 10:03:32 +0100 [thread overview]
Message-ID: <CAMtsiiDrWGKthY52+HT5r19g9EFRG2NHKMD3vni-SeaMNfuGDg@mail.gmail.com> (raw)
In-Reply-To: <1321913175.3253.8.camel@offbook>
On Mon, Nov 21, 2011 at 11:06 PM, Davidlohr Bueso <dave@gnu.org> wrote:
>
> Most of the work I did on supporting v3 was based on the kernel's
> implementation and the mkfs shipped with minix (by ast), so a lot of
> what you say makes sense. I've taken a quick look at the changes and
> most are bugs are pretty straightforward, except:
>
> - mkfs.minix: The total number of zones is limited to 65536 only on V1
> filesystems
>
> Unless I'm missing something, this doesn't really change any logic.
Sorry, probably the commit message is not very well written... However
this commit fixes a very nasty bug, let me explain why....
Look at what the code did *before* my patch:
if (fs_version == 3)
magic = MINIX3_SUPER_MAGIC;
if (fs_version == 2) {
if (namelen == 14)
magic = MINIX2_SUPER_MAGIC;
else
magic = MINIX2_SUPER_MAGIC2;
} else {
if (BLOCKS > MINIX_MAX_INODES)
BLOCKS = MINIX_MAX_INODES;
}
Can you see what happens if fs_version is == 3 ?
The total number of blocks is restricted to a maximum of 65536 both
with V1 and V3 filesystems, this is wrong because the total number of
blocks in V3 is a 32 bit number (the same of V2). With this
realization, it is really simple to fix the bug, and this is exactly
what I did:
if (fs_version == 3)
magic = MINIX3_SUPER_MAGIC;
- if (fs_version == 2) {
+else if (fs_version == 2) {
if (namelen == 14)
magic = MINIX2_SUPER_MAGIC;
else
magic = MINIX2_SUPER_MAGIC2;
} else {
if (BLOCKS > MINIX_MAX_INODES)
BLOCKS = MINIX_MAX_INODES;
}
>
> I'll give the changes a proper test over the weekend.
Ok, thanks.
In case you accept the changes I did, this is the github repository
link with read-only access from where you can pull the changes from:
git://github.com/maurizio-lombardi/util-linux.git
Regards,
--
--------------------
Maurizio Lombardi
next prev parent reply other threads:[~2011-11-22 9:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-21 19:40 mkfs.minix V3 is broken Maurizio Lombardi
2011-11-21 22:06 ` Davidlohr Bueso
2011-11-22 9:03 ` Maurizio Lombardi [this message]
2011-11-22 10:05 ` Maurizio Lombardi
2011-11-22 10:54 ` Karel Zak
2011-11-27 22:03 ` Davidlohr Bueso
2011-11-28 9:27 ` Karel Zak
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