initramfs: scope root device lookup strictly to xvda sysfs (Fixes #11149) - #146
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| udevadm settle --exit-if-exists=/dev/xvda1 | ||
| if [ -e "/dev/disk/by-partlabel/Root\\x20filesystem" ]; then | ||
| ROOT_DEV=$(readlink "/dev/disk/by-partlabel/Root\\x20filesystem") | ||
| ROOT_DEV=$(grep -l "PARTNAME=Root filesystem" /sys/block/xvda/xvda*/uevent 2>/dev/null | tail -n 1) |
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What ordering will the glob produce? Lexographic? If so, then for partitions labeled "Root filesystem" at xdva3 and xvda9, xvda9 will be used as the root. But for partitions at xvda3 and xvda10, xvda3 will be root. Might be confusing. But then again, I estimate an almost 0 probability that someone would hit that. Regardless, I suggest we force an ordering just to be sure that the ordering is actually consistent.
| # On TemplateBasedVM, it is really a device mapper device. | ||
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| SUBSYSTEM=="block", ENV{ID_PART_ENTRY_NAME}=="Root\x20filesystem", ATTR{ro}=="0", SYMLINK+="mapper/dmroot" | ||
| SUBSYSTEM=="block", KERNEL=="xvda*", ENV{ID_PART_ENTRY_NAME}=="Root\x20filesystem", ATTR{ro}=="0", SYMLINK+="mapper/dmroot" |
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For this, there's an assumption that the last seen block device with partition name "Root filesystem" should be dmroot. Is this a valid assumption? Or should be get rid of this udev rule completely and manually add the symlink in the changes above, where we are certain which root device is being used?
Do not look up the root partition via the global /dev/disk/by-partlabel symlink, because when secondary block devices are attached (such as attaching a disk image to a new disposable qube), duplicated partition labels like "Root filesystem" cause udev to point the symlink at the attached device instead of xvda. Look up the partition label strictly under /sys/block/xvda/xvda*/uevent with sort -V to ensure natural numeric ordering. For TemplateVMs, create /dev/mapper/dmroot directly and register the runtime udev rule under /run/udev/rules.d/ so that the mapping persists across switch_root without relying on static partition name matching. Fixes QubesOS/qubes-issues#11149
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Fixes QubesOS/qubes-issues#11149: Attaching block dev to new disposable qube can result in qube using dev as root device
Summary
Scope root partition discovery during early boot strictly to xvda sysfs entries rather than the global by-partlabel symlink.
Key Changes