You have been subscribed to a public bug:
1. create folder by root
2. add wt permission flags to all in that folder
3. flock a file by user in that folder - success
4. flock the same file by root - error: Permission denied
It is somehow important that user have limited access to parent folder (/ in
this example).
test@ubuntu20-04:~$ sudo rm -rf /t_rwt/
test@ubuntu20-04:~$ sudo mkdir /t_rwt
test@ubuntu20-04:~$ sudo chmod a+wt /t_rwt
test@ubuntu20-04:~$ flock /t_rwt/file echo aaa
aaa
test@ubuntu20-04:~$ sudo flock /t_rwt/file echo aaa
flock: cannot open lock file /t_rwt/file: Permission denied
test@ubuntu20-04:~$ ls -las /t_rwt
total 8
4 drwxrwxrwt 2 root root 4096 Apr 28 08:01 .
4 drwxr-xr-x 26 root root 4096 Apr 28 08:00 ..
0 -rw-rw-r-- 1 test test 0 Apr 28 08:01 file
test@ubuntu20-04:~$ id
uid=1000(test) gid=1000(test)
groups=1000(test),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),120(lpadmin),131(lxd),132(sambashare)
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Tags: bot-comment focal
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root cannot flock user file in rwt dir if parent gives limited access
https://bugs.launchpad.net/bugs/1875667
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