Re: Gold Linker Patch: Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715 and in some places called "spectre".

[Florian Weimer <fweimer at redhat dot com>]

On 01/08/2018 07:19 PM, Sriraman Tallam wrote:
> * Regarding what HJ said, unless I misunderstood, I believe he is
> referring to using fno-plt.  We considered that but the problem is the
> indirect jump still exists, but now at the call site.  The mitigation
> would still be necessary at the call site as it is still exposed to
> the attack.

But you'll have to patch GCC anyway to change the opcode sequence for 
indirect jumps (just think of vtable dispatch), and then -fno-plt most 
likely would move the dynamic linker and PLT stubs completely out of the 
equation.

A DSO boundary is not a trust boundary, so this is not comparable to the 
kernel situation at all.  For a generic solution, you need to rewrite 
all indirect function calls.

Thanks,
Florian