linux-kernel - Re: Kernel 4.14: Using dm-verity with squashfs rootfs

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Date:   Mon, 30 Aug 2021 18:55:41 +0200
From:   Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To:     Pintu Agarwal <pintu.ping@...il.com>
Cc:     Mikulas Patocka <mpatocka@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        Phillip Lougher <phillip@...ashfs.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-mtd <linux-mtd@...ts.infradead.org>, dm-devel@...hat.com,
        Kernelnewbies <kernelnewbies@...nelnewbies.org>, agk@...hat.com,
        snitzer@...hat.com, Sami Tolvanen <samitolvanen@...gle.com>
Subject: Re: Kernel 4.14: Using dm-verity with squashfs rootfs - mounting
 issue

Hello,

On Mon, 30 Aug 2021 21:55:19 +0530
Pintu Agarwal <pintu.ping@...il.com> wrote:

> Sorry for coming back to this again..
> Unfortunately, none of the options is working for us with squashfs
> (bootloader, initramfs).
> initramfs have different kinds of challenges because of the partition
> size issue.
> So, our preferred option is still the bootloader command line approach..
> 
> Is there a proven and working solution of dm-verity with squashfs ?
> If yes, please share some references.
> 
> The current problem with squashfs is that we could not append the
> verity-metadata to squashfs, so we store it on a separate volume and
> access it.

Here, it definitely worked to append the hash tree to the squashfs
image and store them in the same partition.

> By specifying it like : /dev/mtdblock53
> 
> Then we get the error like this:
> {
> [    4.950276] device-mapper: init: attempting early device configuration.
> [    4.957577] device-mapper: init: adding target '0 95384 verity 1
> /dev/ubiblock0_0 /dev/mtdblock53 4096 4096 11923 8 sha256
> 16da5e4bbc706e5d90511d2a3dae373b5d878f9aebd522cd614a4faaace6baa3
> aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7 10
> restart_on_corruption ignore_zero_blocks use_fec_from_device
> /dev/mtdblock53 fec_roots 2 fec_blocks 12026 fec_start 12026'
> [    4.975283] device-mapper: verity: sha256 using implementation
> "sha256-generic"
> [    4.998728] device-mapper: init: dm-0 is ready

Could you show the full kernel command line ?

> Do you see any other problem here with dm-verity cmdline or with squashfs ?
> 
> Is squashfs ever proved to be working with dm-verity on higher kernel version ?
> Currently our kernel version is 4.14.

I confirm we used squashfs on dm-verity successfully. For sure on 4.19,
perhaps on older kernels as well.

> Or, another option is to use the new concept from 5.1 kernel that is:
> dm-mod.create = ?

How are you doing it today without dm-mod.create ?

Again, please give your complete kernel command line.

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com