Sorry for the late reply guys, I was not subscribed to the list, just
got the address from the bug report instructions in case the related
package could not be identified, and thought I get an answer directly to
my mailbox xD: https://www.debian.org/Bugs/Reporting.en.html
Back to topic.
I totally forgot to make clear that it is an issue on Debian Bullseye
only. On Buster this would have been recognised much earlier ;).
@Tomas:
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root@VM-Bullseye:/tmp# id
uid=0(root) gid=0(root) groups=0(root)
root@VM-Bullseye:/tmp# >> testfile
-bash: testfile: Permission denied
root@VM-Bullseye:/tmp# dash -c '>> testfile'
dash: 1: cannot create testfile: Permission denied
-------
As said, the issue was first recognised during a Python module install,
so in a totally different environment. My shell is bash as well, but I
can reproduce the issue with any shell or any other language to write to
a file in sticky bit directories.
@Greg
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root@VM-Bullseye:/tmp# id
uid=0(root) gid=0(root) groups=0(root)
root@VM-Bullseye:~# cd /tmp
root@VM-Bullseye:/tmp# df -T
Filesystem Type 1K-blocks Used Available Use% Mounted on
udev devtmpfs 1016164 0 1016164 0% /dev
/dev/sda1 ext4 8189368 584548 7169108 8% /
tmpfs tmpfs 1018568 0 1018568 0% /dev/shm
tmpfs tmpfs 407428 5504 401924 2% /run
tmpfs tmpfs 5120 0 5120 0% /run/lock
tmpfs tmpfs 4096 0 4096 0% /sys/fs/cgroup
tmpfs tmpfs 1018880 37432 981448 4% /tmp
tmpfs tmpfs 51200 8 51192 1% /var/log
root@VM-Bullseye:/tmp# cd /root
root@VM-Bullseye:~# mkdir testdir
root@VM-Bullseye:~# chmod 1777 testdir
root@VM-Bullseye:~# > testdir/testfile
root@VM-Bullseye:~# chown www-data testdir/testfile
root@VM-Bullseye:~# > testdir/testfile
-bash: testdir/testfile: Permission denied
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The issue is not related to the file system and not related to the
kernel version. As said I tested in on RPi with their current stable
Linux 5.4 (now with a second recent update) and on Bullseye with now as
well two kernel versions. But to be sure, I'll downgrade the kernel to a
previous major version, probably from Buster backports, just to be sure.
This is a bug clearly, I'm just not sure, if kernel and file system and
shell/environment does not play a role, which part of the OS does, i.e.
is sitting between userland programs and kernel/fs driver to verify UNIX
permissions.
Best regards,
Micha
