lsattr loading modules, changing permissions of device nodes

[Marc Haber]

Hi,

I have recently noted that my unstable installations are doing strange
things with /dev. For example, see here /dev/btrfs-control changing
group and permissions on a pure lsattr:

(freshly rebooted system without a btrfs filesystem)
|[3/3719]mh at emptysid86:~ $ ls -al /dev/btrfs-control 
|crw------- 1 root root 10, 234 Mär 16 19:17 /dev/btrfs-control
|[4/3720]mh at emptysid86:~ $ sudo lsattr /dev/btrfs-control 
|[sudo] password for mh on emptysid86: 
|lsattr: Operation not supported While reading flags on
|/dev/btrfs-control
|[5/3721]mh at emptysid86:~ $ ls -al /dev/btrfs-control
|crw-rw---- 1 root disk 10, 234 Mär 16 19:18 /dev/btrfs-control
|[6/3722]mh at emptysid86:~ $ less /usr/share/doc/udev/

See here vcs* device nodes appearing when lsattr is invoked on a tty:
|[8/3724]mh at emptysid86:~ $ ls -al /dev/*24*
|crw--w---- 1 root tty 4, 24 Mär 16 19:17 /dev/tty24
|[9/3725]mh at emptysid86:~ $ sudo lsattr /dev/tty24
|lsattr: Operation not supported While reading flags on /dev/tty24
|1 [10/3726]mh at emptysid86:~ $ ls -al /dev/*24*
|crw--w---- 1 root tty 4,  24 Mär 16 19:40 /dev/tty24
|crw-rw---- 1 root tty 7,  24 Mär 16 19:40 /dev/vcs24
|crw-rw---- 1 root tty 7, 152 Mär 16 19:40 /dev/vcsa24
|crw-rw---- 1 root tty 7,  88 Mär 16 19:40 /dev/vcsu24
|[11/3727]mh at emptysid86:~ $

See here the tun kernel module being loaded on an lsattr on
/dev/net/tun:
|[11/3727]mh at emptysid86:~ $ sudo lsmod | grep tun
|1 [12/3728]mh at emptysid86:~ $ sudo lsattr /dev/net/tun
|lsattr: File descriptor in bad state While reading flags on /dev/net/tun
|1 [13/3729]mh at emptysid86:~ $ sudo lsmod | grep tun
|tun                    53248  0
|[14/3730]mh at emptysid86:~ $

I suspect this has something to do with the recent udev update in
unstable, the behavior has first appeared in unstable and recently
migrated to testing.  I noticed this behavior while working on the aide
package, hence I suspect that not many peope even notice.

Now friendly and innocent questions towards the udev maintainers:
* Do you see similiar behavior on your systems?
* If yes, is this intended behavior?
* Why does, for example, the /dev/btrfs-control device node get created
  with one set of owner/mode and then gets converted to a different one
  when someone accesses it? btrfs-progs are not installed, btrfs is not
  in use.

Any ideas? I would appreciate your opinion and comments.

Greetings
Marc

P.S.: Please cc me on replies, I am not subscribed to
pkg-systemd-maintainers

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Marc Haber         | "I don't trust Computers. They | Mailadresse im Header
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