On 17/07/2019 19:06, Tom Eccles wrote: > Hello, > > I have a question about veritysetup using forward error correction. > > I created my dm-verity volume using > > veritysetup --check-at-most-once --fec-device /dev/vdc --fec-roots 24 format > /dev/vdb1 /dev/vdd > > Then I introduce a single bit error into /dev/vdb1. > > If I then open the dm-verity device using > > veritysetup --fec-device /dev/vdc --fec-roots 24 open /dev/vdb1 vroot > /dev/vdd <hash> > > When I mount the device and inspect the corrupted file, the single bit error > cannot be corrected: > [ 108.994804] device-mapper: verity-fec: 254:17: FEC 19300352: failed to > correct: -74 > [ 108.994834] device-mapper: verity: 254:17: data block 273411 is corrupted > > However, if I verify the whole device using veritysetup it succeeds: > > veritysetup --fec-device /dev/vdc --fec-roots 24 verify /dev/vdb1 /dev/vdd > <hash> > Verification failed at position 1119891456. > Verification of data area failed. > Found 1 repairable errors with FEC device > > So I suspect that I have the wrong flags to veritysetup open. Can anybody > see where I am going wrong? Well, the FEC code in userspace and kernel differs, it is quite possible that there could be some misconfiguration or a bug. Please be sure you are testing access to the image and not some cached data in meory - better flush all caches between runs with the command "echo 3 > /proc/sys/vm/drop_caches". If you can still reproduce it, please send version of the utility and kernel (and --debug output as suggested in another mail) and if you have some data/hash/fec images that can be used to reproduce it, let me know where I can find it. Thanks, Milan _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx https://www.saout.de/mailman/listinfo/dm-crypt
