File permissions lost during send/receive?

[Marc Joliet <marcec@gmx.de>]

[-- Attachment #1: Type: text/plain, Size: 2250 bytes --]

Hi list,

(Preemptive note: this was with btrfs-progs 4.15.1, I have since upgraded to 
4.17.  My kernel version is 4.14.52-gentoo.)

I recently had to restore the root FS of my desktop from backup (extent tree 
corruption; not sure how, possibly a loose SATA cable?).  Everything was fine, 
even if restoring was slower than expected.  However, I encountered two files 
with permission problems, namely:

- /bin/ping, which caused running ping as a normal user to fail due to missing 
permissions, and

- /sbin/unix_chkpwd (part of PAM), which prevented me from unlocking the KDE 
Plasma lock screen; I needed to log into a TTY and run "loginctl unlock-
session".

Both were easily fixed by reinstalling the affected packages (iputils and 
pam), but I wonder why this happened after restoring from backup.

I originally thought it was related to the SUID bit not being set, because of 
the explanation in the ping(8) man page (section "SECURITY"), but cannot find 
evidence of that -- that is, after reinstallation, "ls -lh" does not show the 
sticky bit being set, or any other special permission bits, for that matter:

% ls -lh /bin/ping /sbin/unix_chkpwd 
-rwx--x--x 1 root root 60K 22. Jul 14:47 /bin/ping*                                                                                                                                                                                                                            
-rwx--x--x 1 root root 31K 23. Jul 00:21 /sbin/unix_chkpwd*

(Note: no ACLs are set, either.)

I do remember the qcheck program (a Gentoo-specific program that checks the 
integrity of installed packages) complaining about wrong file permissions, but 
I didn't save its output, and there's a chance it *might* have been because I 
ran qcheck without root permissions :-/ .

I vaguely remember some patches and/or discussion regarding permission 
transfer issues with send/receive on this ML, but didn't find anything after 
searching through my Email archive, so I might be misremembering.

Does anybody have any idea what possibly went wrong, or any similar experience 
to speak of?

Greetings
-- 
Marc Joliet
--
"People who think they know everything really annoy those of us who know we
don't" - Bjarne Stroustrup

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 833 bytes --]