Description of problem: A data corrupter bug has been identified in the following nbdkit filters: https://libguestfs.org/nbdkit-cow-filter.1.html https://libguestfs.org/nbdkit-cache-filter.1.html It's quite subtle, but it affects modular virt-v2v and was picked up by Ming Xie during testing. The full bug is described in this link, as well as a simple way to reproduce it, and the fix: https://listman.redhat.com/archives/libguestfs/2021-August/msg00044.html Version-Release number of selected component (if applicable): All versions of nbdkit since 1.14 up to 1.27.4 How reproducible: 100% Steps to Reproduce: 1. See link above.
Reproduce the bug with nbdkit-1.26.2-2.el9.x86_64 Steps to reproduce: 1. # nbdkit --filter=cow data "33 * 100000" --run 'nbdsh -u $uri -c "h.trim(100000, 0)" ; nbdcopy $uri - | hexdump -C' 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00010000 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 21 |!!!!!!!!!!!!!!!!| * 000186a0 Verify the bug with nbdkit-1.26.3-1.el9.x86_64 Steps: 1.# nbdkit --filter=cow data "33 * 100000" --run 'nbdsh -u $uri -c "h.trim(100000, 0)" ; nbdcopy $uri - | hexdump -C' 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 000186a0 Result: The bug has been fixed, so move the bug from ON_QA to VERIFIED