I follow a tutorial to secure my /etc/fstab file. This is a certain part about /var and /tmp

UUID=XXXX-XXXX-XXXX /var ext4 defaults,nodev,nosuid,noexec 1 2
UUID=ZZZZ-ZZZZ-ZZZZ /tmp ext4 defaults,nodev,nosuid,noexec 1 2

I executed the following commands to test the configuration :

touch /tmp/testFile
chmod u+s /tmp/testFile

I was expecting an error message but nothing... Is it normal ? Is it dangerous ?

  • 1
    Did you check with ls /tmp/testFile if you have SUID on file? – Romeo Ninov Jan 8 at 14:48

nosuid doesn’t prevent setting the bits; it means that they don’t have any effect. (That way, previously-set bits are also rendered ineffective.)

Setting the bits is only dangerous if the file system is later mounted without nosuid; but if anyone has sufficient access to set those bits on your file system, you’ve lost anyway.

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