exec_as_uid sometimes incorrectly drops privileges before returning

[Gord-Butler]

During an attempt to upgrade ports (version 2.5.2 on OSX 10.9), avahi could not be rebuilt because MacPorts couldn't build a directory. The error message given is below.

Error: Couldn't activate avahi 0.7_3+gtk+gtk3+quartz: can't create directory "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_net_avahi": permission denied
Error: rev-upgrade failed: Error rebuilding avahi

[kencu (Ken)]

This has been happening to me lately on various systems and with various ports, most often dbus.

Try just doing sudo port activate avahi and then select the right one (the last one) from the list that pops up. This has worked for me in every case so far.

[jmroot (Joshua Root)]

Could you attach the log please?

[jmroot (Joshua Root)]

This problem can't be reproduced on High Sierra. It will be very difficult to investigate further without a log or debug output.

[Gord-Butler]

I couldn't find a log. All I got was the message stating it couldn't create a folder at the location stated in the error message.

[jmroot (Joshua Root)]

The log path will be shown by port logfile avahi. If there isn't one then please run the command with the -d option to generate debug output.

[Gord-Butler]

I ran the upgrade with the -d option. This is the output.

sudo port upgrade avahi -d
--->  Scanning binaries for linking errors
--->  Found 17 broken files, matching files to ports     
--->  Found 4 broken ports, determining rebuild order
You can always run 'port rev-upgrade' again to fix errors.
The following ports will be rebuilt:
 avahi @0.7+gtk+gtk3+quartz
 gegl @0.2.0-20180218+quartz
 opencv @3.3.1
 gmic @2.2.2
Continue? [Y/n]: Y
Error: Couldn't activate avahi 0.7_3+gtk+gtk3+quartz: can't create directory "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_net_avahi": permission denied
Error: rev-upgrade failed: Error rebuilding avahi
Error: Follow https://guide.macports.org/#project.tickets to report a bug.

I was able to activate it with sudo port activate avahi and selecting the last option on the list, though.

[jmroot (Joshua Root)]

Sorry, the -d needs to go between port and upgrade. Putting it at the end attempts to turn off a variant called "d".

[jmroot (Joshua Root)]

I may have found the problem.

[jmroot (Joshua Root)]

In 4b36e605d76fa3a423b4e35a6722ade4185ffa4f/macports-base (master):

Fix restoring previous euid in exec_as_uid

Fixes: #56721

[jmroot (Joshua Root)]

In 5766cfed60233f3ffd7cc7e582bf81d47490c55f/macports-base (release-2.5):

Fix restoring previous euid in exec_as_uid

Fixes: #56721
(cherry picked from commit 4b36e605d76fa3a423b4e35a6722ade4185ffa4f)