should Unix refuse to execute writable binaries?

[Barry Shein]

Any writeable, public executable is a hazard, most users consider
their own files valuable and such executables are a hazard to them as
they run with their own privs. It's somewhat admin-o-centric to think
there's something special about setuid/setgid, just a different form
of damage possible (and system disruption is fairly possible from even
non-priv'd accounts, for example a hacked program which fills /tmp.)

The only idea that comes to mind would be something analogous to the
umask() indicating which bits can and cannot be set on an executable,
tho I suspect some thought will reveal that the problem is more subtle
than that, but something like xmask(022) might help.
-- 
        -Barry Shein

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