[dm-crypt] veritysetup verify successful but mount fails with new kernel

Mircea Gliga mircea.gliga at vitheia.com
Thu Jan 25 11:51:08 CET 2018


We are using dm-verity for a squashfs root file system.
Using kernel 4.8.4 everything was ok, after upgrading to kernel 4.14.14 
mount fails, even though the `veritysetup verify` command validates the 
image.


# veritysetup verify /dev/mmcblk0p5 /dev/mmcblk0p6 --hash-offset 4096 
d35f95a4
b47c92332fbcf5aced9c4ed58eb2d5115bad4aa52bd9d64cc0ee676b --debug
# cryptsetup 1.7.4 processing "veritysetup verify /dev/mmcblk0p5 
/dev/mmcblk0p6 --hash-offset 4096 
d35f95a4b47c92332fbcf5aced9c4ed58eb2d5115bad4aa52bd9d64cc0ee676b --debug"
# Running command verify.
# Allocating crypt device /dev/mmcblk0p6 context.
# Trying to open and read device /dev/mmcblk0p6 with direct-io.
# Initialising device-mapper backend library.
# Trying to load VERITY crypt type from device /dev/mmcblk0p6.
# Crypto backend (OpenSSL 1.0.2m  2 Nov 2017) initialized in cryptsetup 
library version 1.7.4.
# Detected kernel Linux 4.14.14-yocto-standard armv7l.
# Reading VERITY header of size 512 on device /dev/mmcblk0p6, offset 4096.
# Setting ciphertext data device to /dev/mmcblk0p5.
# Trying to open and read device /dev/mmcblk0p5 with direct-io.
# Activating volume [none] by volume key.
# Trying to activate VERITY device [none] using hash sha256.
# Verification of data in userspace required.
# Hash verification sha256, data device /dev/mmcblk0p5, data blocks 
10462, hash_device /dev/mmcblk0p6, offset 2.
# Using 2 hash levels.
# Data device size required: 42852352 bytes.
# Hash device size required: 348160 bytes.
# Verification of data area succeeded.
# Verification of root hash succeeded.
# Releasing crypt device /dev/mmcblk0p6 context.
# Releasing device-mapper backend.
Command successful.


# veritysetup create vroot /dev/mmcblk0p5 /dev/mmcblk0p6 --hash-offset 
4096 d3
5f95a4b47c92332fbcf5aced9c4ed58eb2d5115bad4aa52bd9d64cc0ee676b --debug

# mount -o ro /dev/mapper/vroot /mnt/
device-mapper: verity: 179:5: metadata block 2 is corrupted
EXT4-fs (dm-0): unable to read superblock
device-mapper: verity: 179:5: metadata block 2 is corrupted
EXT4-fs (dm-0): unable to read superblock
device-mapper: verity: 179:5: metadata block 2 is corrupted
EXT4-fs (dm-0): unable to read superblock
device-mapper: verity: 179:5: metadata block 2 is corrupted
SQUASHFS error: squashfs_read_data failed to read block 0x0
squashfs: SQUASHFS error: unable to read squashfs_super_block
device-mapper: verity: 179:5: metadata block 2 is corrupted
FAT-fs (dm-0): unable to read boot sector
mount: mounting /dev/mapper/vroot on /mnt/ failed: Input/output error

Same error message appears in dmesg.
The above commands were run on the target device.

On my *host* machine, Debian 8 (kernel 3.16.0-5), using the files which 
eventually ended up in /dev/mmcblk0p5 and /dev/mmcblk0p6,
I was able to set up everything working:

# veritysetup create vroot rootfs-image.squashfs rootfs-image.hashtbl 
--hash-offset 4096 
d35f95a4b47c92332fbcf5aced9c4ed58eb2d5115bad4aa52bd9d64cc0ee676b
# mount /dev/mapper/vroot /tmp/mnt

Any help is appreciated.

Thanks and regards


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