[bug #61764] Unwritable /dev/shm bug

[Boud Roukema]

URL:
  <https://savannah.nongnu.org/bugs/?61764>

                 Summary: Unwritable /dev/shm bug
                 Project: Maneage
            Submitted by: boud
            Submitted on: Tue 04 Jan 2022 08:28:33 PM UTC
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

In the 'reproduce/software/shell/configure.sh' script that
fixes bug https://savannah.nongnu.org/bugs/?60819, we first
create a directory, and then create
a test file 'shm-execution-check.sh' in the new subdirectory
of '/dev/shm' and then check if that script can be run
by the user. See the section starting around lines 1304. [1]

Hypothetically, a system could have the '/dev/shm' device
but not permit the particular user to create directories and files there.
(Different users might be given different rights,
for example, or this might be a root-only RAM fs.) 

In that case, we don't want a fatal error, because we have the
safe fallback of not using /dev/shm.

I've tested this and there is a failure as expected.

I've put a proposed fix that seems to me to work correctly in all
cases.

To test the failure in commit 5641f4e and to see if commit 7d14eb7 [2] works
correctly, try various versions of


sudo mount -o remount,noexec /dev/shm
sudo mount -o remount,exec /dev/shm
sudo mount -o remount,ro /dev/shm
sudo mount -o remount,rw /dev/shm


and check what happens in _/dev/shm_ in the various cases, as 
well as whether the _./project configure_ script behaves as expected.

[1]
https://gitlab.com/maneage/project-dev/-/blob/maneage/reproduce/software/shell/configure.sh#L1304

[2]
https://gitlab.com/maneage/project-dev/-/commit/7d14eb7a585bbd35fb2a8ed2d75d1da8a5a388b7




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