android modified su binary failes on setgid

Question

I have created a custom su binary for testing purposes.

I have copied the binary to /system/xbin/mod_su

I have changed the files permissions with chmod 6755 /system/xbin/mod_su,

but still when I run the binary as a non-root user I fail on setgid(0) with 'Operation not permitted1'

Any ideas why this could happen ?

isn't 6755 permmisons enough ?

Answer 1

Did you chown root.root it before chmod?