linux-ext4 - Re: flashing large eMMC partitions with ext4

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: <134141.91415.qm@web4210.mail.ogk.yahoo.co.jp>
Date:	Thu, 28 Jul 2011 01:40:48 +0900 (JST)
From:	Round Robinjp <roundrobinjp@...oo.co.jp>
To:	Ted Ts'o <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: flashing large eMMC partitions with ext4

> > The flash will then contain _random_ data in the non-used blocks.
> > That is not a problem, right?
> 
> Nope.  So long as the previously written (random) data on the card
> doesn't contain anything security sensitive.

I understood.

> > Although I have very small amount of files in my 4G image,
> > I see that the image has almost no zero-filled blocks.
> > Is that normal for ext4?
> 
> It depends on how you created the image.

I create the image like this:

dd if=/dev/zero of=a.img bs=4096 count=1048576
mkfs.ext4 a.img
mount -t ext4 -o loop a.img /mnt
cp -a /foo/* /mnt/
umount /mnt

> > Can zerofree.c recognize them as non-used blocks?
> 
> Yes, it uses the block allocation bitmaps to understand what is used
> and non-used.

Great.

Thanks
Round
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html