On Tue, May 20, 2025 at 07:57:31AM +0200, Salvatore Bonaccorso wrote: > Hi > > In Debian Roland Clobus reported a regression with setting up loop > devices from a backing squashfs file lying on read-only mounted target > directory from a iso. > > The original report is at: > https://bugs.debian.org/1106070 > > Quoting the report: > > On Mon, May 19, 2025 at 12:15:10PM +0200, Roland Clobus wrote: > > Package: linux-image-6.12.29-amd64 > > Version: 6.12.29-1 > > Severity: important > > X-Debbugs-Cc: debian-amd64@xxxxxxxxxxxxxxxx > > User: debian-amd64@xxxxxxxxxxxxxxxx > > Usertags: amd64 > > X-Debbugs-Cc: phil@xxxxxxxxx > > User: debian-qa@xxxxxxxxxxxxxxxx > > Usertags: openqa > > X-Debbugs-Cc: debian-boot > > > > Hello maintainers of the kernel, > > > > The new kernel (6.12.29) has a modified behaviour (compared to 6.12.27) for > > the loop device. > > > > This causes the Debian live images (for sid) to fail to boot. > > > > The change happened between 20250518T201633Z and 20250519T021902Z, which > > matches the upload of 6.12.29 (https://tracker.debian.org/news/1646619/accepted-linux-signed-amd64-612291-source-into-unstable/) > > at 20250518T230426Z. > > > > To reproduce: > > * Download the daily live image from https://openqa.debian.net/tests/396941/asset/iso/smallest-build_sid_20250519T021902Z.iso > > * Boot into the live image (the first boot option) > > * Result: an initramfs shell (instead of a live system) -> FAIL > > * Try: `losetup -r /dev/loop1 /run/live/medium/live/filesystem.squashfs` > > * Result: `failed to set up loop device: invalid argument` -> FAIL > > * Try: `cp /run/live/medium/live/filesystem.squashfs /` > > * Try: `losetup -r /dev/loop2 /filesystem.squashfs` > > * Result: `loop2: detected capacity change from 0 to 1460312` -> PASS > > > > It appears that the loopback device cannot be used any more with the mount > > /run/live/medium (which is on /dev/sr0). > > > > I've verified: the md5sum of the squashfs file is OK. > > > > The newer kernel is not in trixie yet. > > > > With kind regards, > > Roland Clobus > > A short reproducer is as follows: > > iso="netinst.iso" > url="https://openqa.debian.net/tests/396941/asset/iso/smallest-build_sid_20250519T021902Z.iso"; > if [ ! -e "${iso}" ]; then > wget "${url}" -O "${iso}" > fi > mountdir="$(mktemp -d)" > mount -v "./${iso}" "${mountdir}" > losetup -v -r -f "${mountdir}/live/filesystem.squashfs" > loosetup -l > > resulting in: > > mount: /tmp/tmp.HgbNe7ek3h: WARNING: source write-protected, mounted read-only. > mount: /dev/loop0 mounted on /tmp/tmp.HgbNe7ek3h. > losetup: /tmp/tmp.HgbNe7ek3h/live/filesystem.squashfs: failed to set up loop device: Invalid argument > NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO LOG-SEC > /dev/loop0 0 0 1 0 /root/netinst.iso 0 512 > > Reverting 184b147b9f7f ("loop: Add sanity check for read/write_iter") > on top of 6.12.29 fixes the issue: > > mount: /tmp/tmp.ACkkdCdYvB: WARNING: source write-protected, mounted read-only. > mount: /dev/loop0 mounted on /tmp/tmp.ACkkdCdYvB. > NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO LOG-SEC > /dev/loop1 0 0 0 1 /tmp/tmp.ACkkdCdYvB/live/filesystem.squashfs 0 512 > /dev/loop0 0 0 1 0 /root/netinst.iso 0 512 > > For completeness, netinst.iso is a iso9660 fstype with mount options > "ro,relatime,nojoliet,check=s,map=n,blocksize=2048,iocharset=utf8". > > #regzbot introduced: 184b147b9f7f > #regzbot link: https://bugs.debian.org/1106070 Just tested: The regression exists as well in 6.15-rc7 so it is not specific to the stable 6.12.y update. Regards, Salvatore
