Thanks again for feedback ! Yes, I can do some additional tests in order to isolate the problem. I'm not that familiar with the code responsible for this so I'll ask for your help with a patch. It will be quicker that way. Best regards Mircea On Sat, Feb 24, 2018 at 10:59 AM, Gilad Ben-Yossef wrote: > Hi, > > I'm adding the linux crypto mailing list because it seems relevant. > > > On Fri, Feb 23, 2018 at 2:25 PM, Gigi W wrote: > > Thanks for the input! > > > > See below > > > > > > On Fri, Feb 23, 2018 at 10:53 AM Gilad Ben-Yossef > > wrote: > >> > >> On Fri, Feb 23, 2018 at 10:30 AM, Gigi W wrote: > >> > Hi > >> > > >> > I'm having some trouble using dm-verity for a squashfs root file > system > >> > that > >> > seems to be related to the > >> > Atmel SHA hw accelerator in the kernel, CONFIG_CRYPTO_DEV_ATMEL_SHA > >> > > >> > Some info about my setup: > >> > * I'm using a board with a SAMA5D4 CPU. > >> > * I'm using Yocto rocko for building an image for that device. > >> > > >> > The idea is that Using the 4.14.14 Kernel, Integrity checking using > >> > Kernel > >> > crypto fails with Atmel SHA hw accelerator enabled in kernel. > >> > By disabling it, `CONFIG_CRYPTO_DEV_ATMEL_SHA=n`, and using the > software > >> > sha256 algo, integrity checking works as expected. > >> > This is my kernel config [3] > >> > > >> > Using the 4.8.4 Kernel and Atmel SHA hw accelerator enabled, > everything > >> > was > >> > ok. > >> > > >> > This is what triggers the error during verified boot: > >> > > >> > status=`veritysetup create vroot $root_dev $verity_dev --hash-offset > >> > $hashoffset $root_hash` > >> > > >> > mount /dev/mapper/vroot /mnt/ > >> > mount_ok=`cat /proc/mounts | grep mnt` > >> > if [ -z "$mount_ok" ] ; then > >> > echo "Failed to mount $root_dev on mnt/" > >> > else > >> > echo "Switch rootfs" > >> > exec switch_root -c /dev/console /mnt /sbin/init > >> > fi > >> > > >> > The mount operation fails: > >> > > >> > device-mapper: verity: 179:4: metadata block 2 is corrupted > >> > EXT4-fs (dm-0): unable to read superblock > >> > device-mapper: verity: 179:4: metadata block 2 is corrupted > >> > EXT4-fs (dm-0): unable to read superblock > >> > device-mapper: verity: 179:4: metadata block 2 is corrupted > >> > EXT4-fs (dm-0): unable to read superblock > >> > device-mapper: verity: 179:4: 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: 179:4: 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 > >> > Failed to mount /dev/mmcblk0p4 on mnt/ > >> > reboot: Restarting system > >> > Reboot failed -- System halted > >> > > >> > Using veritysetup to verify the integrity against the hashes is > >> > successful, > >> > as it's not using the kernel for that ... > >> > > >> > > >> > So it looks like it something changed from 4.8.4 to 4.14.14. > >> > >> If I am not mistaken the Atmel SHA hw accelerator is an async (read: > >> off CPU) crypto accelerator. > >> Up until 4.12 (I think...) DM-Verity did not use async crypto > >> accelerators (even if present and have high > >> priority). I've changed this is commit d1ac3ff008fb ("dm verity: > >> switch to using asynchronous hash crypto API"). > > > > > > This would explain some things, like the same speeds while reading from a > > verity device, having the CONFIG_CRYPTO_DEV_ATMEL_SHA enabled and then > > disabled, on the 4.8.4 kernel -> it was always using the sync API. > > > >> > >> > >> Is it possible that whatever issue you are seeing has always been > >> there and when DM-Verity started using > >> async. accelerators it was only exposed? > > > > > > It looks like it. > > > > From my understandings + tests described above, Atmel SHA hw accelerator > > works correctly - output hashes are ok, dm-verity with other async crypto > > accelerators is working ok, > > but dm-verity + Atmel SHA hw accelerator don't play nice together. > > > > I couldn't find anyone else complaining about this. > > > > I agree that that the possibility that there is something wrong in the > Atmel SHA accelerator is one possible direction. > The other one is that there is something wrong in DM-Verity that only > manifests under certain conditions when working with async crypto HW > providers. > I don't think it is the case, because I tested DM-Verity after my > changes with the CryptoCell async HW provider and did not get any > other bug reports, but I'd like to be sure. > > Can you do a little experiment? add debug printk to show the data > being hashed, the hash produced by atmel and the expected > pre-calculated hash. > > If the theory that there is something wrong with atmel accelerator, we > can calculate the hash on the data with other means (software) and > should get a different hash. > > If you are having trouble adding the printk's in the right place let > me know and I'll create a patch for you to test. > > Cheers, > Gilad > > > -- > Gilad Ben-Yossef > Chief Coffee Drinker > > "If you take a class in large-scale robotics, can you end up in a > situation where the homework eats your dog?" > -- Jean-Baptiste Queru >