[Bug 1092715] Re: udevadm trigger --action=change not working since quantal?

[Serge Hallyn]

I'm now convinced this is a kernel bug.

If I do
   touch xxx
   setfacl -m g::--- xxx
   strace -f -ooutput chmod g+rw xxx
   getfacl xxx

I see that the group acl for xxx is changed to include rw, and the file
'output' shows that chmod simply calls the fchmodat syscall, which uses
notify_change to update the acl.

If I do
   # make sure to be logged into console
   sudo apt-get purge qemu-kvm
   sudo modprobe kvm_intel
   sudo apt-get install qemu-kvm
   getfacl xxx
   # see that group acl is still ---
   sudo chmod g+rw /dev/kvm
   # see that group acl is still ---

So the kernel is meant to be updating the acl in fchmodat, but is not
doing it.  I will try a xfs-backed VM to see if the bug is in ext4
itself, or in the generic fs code.

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https://bugs.launchpad.net/bugs/1092715

Title:
  udevadm trigger --action=change not working since quantal?

Status in “linux” package in Ubuntu:
  Incomplete
Status in “udev” package in Ubuntu:
  Confirmed

Bug description:
  For bug 1057024, we have qemu-kvm postinst call udevadm trigger
  --action=change.  This is to make udev recalculate permissions for
  /dev/kvm based on the new /lib/udev/rules.d/40-qemu-kvm.rules file.

  In precise, this causes /dev/kvm's acls to be correctly set so that
  group has rw permissions.

  In quantal, with the exact same rules file, it does not.  After a
  reboot, permissions are set correctly.  But manually running udevadm
  trigger --subsystem=misc --action=change (or variations of that) does
  not change the group acl.  It changes the group ownership, and part of
  the acl, but not the group acl.

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