How can I guard my system against stack buffer overflow exploits?

By default, the Solaris kernel maps the system stack RWX;
this behaviour is mandated by the SPARC V8 ABI. Since an
non-executable stack gets in the way of certain classes of
security bug exploits, a feature was added to Solaris 2.6 that
allows system administrators to remove the "X" protection from
the stack.

To enable this feature, add the following to /etc/system:

* Foil certain classes of bug exploits
set noexec_user_stack = 1

* Log attempted exploits
set noexec_user_stack_log = 1

This is no general "cure-all" protection for buffer overflow exploits.
It may also break certain SPARC V8 ABI conforming programs.

This feature also requires hardware support; it is only available on
UltraSPARC (sun4u), sun4d and sun4m systems.

The SPARC V9 ABI no longer maps the stack executable, so 64 bit
applications have less to worry about. 32-bit applications running
on a 64-bit kernel are not so lucky.

This feature also works on x86 family CPUs which support the
"NX" (no execute) page table bit. In Solaris 10, we've marked the
datasegment and stacksegment of Solaris executables no-execute.
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