udev: don't import parent ID_FS_ data on partitions

When probing partitions, we inherit important information from the parent
disk device such as ID_MODEL, and usage of such properties is seen to
be acceptable and well established.

However, we need to exclude filesystem information from the properties
that get inherited. Information about the device content should not be
passed on in this way.

For example, Linux distro install media commonly uses an ISO filesystem
plus a partition table. The ISO filesystem is detected on the main disk
device, but we should not pass down those details to the partitions,
some or all of which may be pointing at storage areas completely distinct
from the ISO filesystem.

This is particularly problematic when adding new partitions on media
set up in this way (since the new partitions are then reported to contain
the parent device's ISO filesystem), or when dealing with more unusual
hybrid ISO layouts. The inaccuracy of information here inversely affects
users of blkid and udev's persistent storage symlinks.

Exclude ID_FS_* properties from the inheritance chain to avoid these
problems.

Fixes: #14408

1 files changed, 16 insertions, 2 deletions

diff --git a/rules.d/60-persistent-storage.rules b/rules.d/60-persistent-storage.rules
index 7802b1c94f..01586690bd 100644
--- a/rules.d/60-persistent-storage.rules
+++ b/rules.d/60-persistent-storage.rules
@@ -12,8 +12,22 @@ KERNEL!="loop*|mmcblk*[0-9]|msblk*[0-9]|mspblk*[0-9]|nvme*|sd*|sr*|vd*|xvd*|bcac
 # ignore partitions that span the entire disk
 TEST=="whole_disk", GOTO="persistent_storage_end"
 
-# for partitions import parent information
-ENV{DEVTYPE}=="partition", IMPORT{parent}="ID_*"
+# For partitions import parent disk ID_* information, except ID_FS_*.
+#
+# This is particularly important on media where a filesystem superblock and
+# partition table are found on the same level, e.g. common Linux distro ISO
+# installation media.
+#
+# In the case where a partition device points to the same filesystem that
+# was detected on the parent disk, the ID_FS_* information is already
+# present on the partition devices as well as the parent, so no need to
+# propagate it. In the case where the partition device points to a different
+# filesystem, merging the parent ID_FS_ properties would lead to
+# inconsistencies, so we avoid doing so.
+ENV{DEVTYPE}=="partition", \
+  IMPORT{parent}="ID_[!F]*", IMPORT{parent}="ID_", \
+  IMPORT{parent}="ID_F[!S]*", IMPORT{parent}="ID_F", \
+  IMPORT{parent}="ID_FS[!_]*", IMPORT{parent}="ID_FS"
 
 # NVMe
 KERNEL=="nvme*[0-9]n*[0-9]", ATTR{wwid}=="?*", SYMLINK+="disk/by-id/nvme-$attr{wwid}"