Package: xfsprogs Version: 4.9.0+nmu1 Severity: minor Dear Maintainer,
I am currently in the process of changing the underlying encryption on many devices. This involves copying data off, changing encryption parameters, copying data back. Changing the underlying encryption (e.g. from aes-cbc-essiv:sha256 to aes-xts-plain64) should pretty much randomly scramble the existing data, and looking at the first blocks, this seems to be the case. However, mkfs.xfs has roughly a 30% chance here of misdetecting random data as "atari partition table format" (this seems to increase with the size of the device, the smallest device I used was 8TB): mkfs.xfs: /dev/mapper/nls112-11 appears to contain a partition table (atari). Which of course is somewhat unsettling :) Looking at http://drac030.krap.pl/APT_spec.pdf, the block doesn't resemble an atari partition at all (no APT magic string and so on). Given the high chance of msidetecting random data for a valid partition, I think the atari partition table detection code should either be improved or disabled by default, as it surely generates many more false positives and true detections. I haven't investigated this in more detail, but it is possible that the code only checks wether a partition fits into the disk, and this would be 100% the case with devices >2TB. Indeed, I can easily reproduce this by running this multiple times: lvcreate -n tempbig -L 4.5t vg_nlsb112 # once only of course :) dd if=/dev/urandom of=/dev/vg_nlsb112/tempbig bs=4096 count=512 mkfs.xfs /dev/vg_nlsb112/tempbig I get a roughly one in seven chance of getting an atari partition table. -- System Information: Debian Release: 9.6 APT prefers stable APT policy: (990, 'stable'), (500, 'unstable-debug'), (500, 'testing-debug'), (500, 'stable-updates'), (500, 'stable-debug'), (500, 'unstable'), (500, 'testing'), (1, 'experimental-debug'), (1, 'experimental') Architecture: amd64 (x86_64) Foreign Architectures: i386, x32 Kernel: Linux 4.18.20-041820-generic (SMP w/8 CPU cores) Locale: LANG=C, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=C (charmap=UTF-8) Shell: /bin/sh linked to /usr/bin/bash Init: systemd (via /run/systemd/system) Versions of packages xfsprogs depends on: ii libblkid1 2.29.2-1+deb9u1 ii libc6 2.27-8 ii libreadline5 5.2+dfsg-3+b1 ii libuuid1 2.29.2-1+deb9u1 xfsprogs recommends no packages. Versions of packages xfsprogs suggests: ii acl 2.2.52-3+b1 ii attr 1:2.4.47-2+b2 pn quota <none> ii xfsdump 3.1.6+nmu2+b1 -- no debconf information
