Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function

On Fri, 2019-06-07 at 12:03 -0700, Dave Hansen wrote:

On 6/6/19 1:09 PM, Yu-cheng Yu wrote:

quoted

+	modify_fpu_regs_begin();
+	rdmsrl(MSR_IA32_U_CET, r);
+	r |= (MSR_IA32_CET_LEG_IW_EN | bitmap);
+	wrmsrl(MSR_IA32_U_CET, r);
+	modify_fpu_regs_end();

Isn't there a bunch of other stuff in this MSR?  It seems like the
bitmap value would allow overwriting lots of bits in the MSR that have
nothing to do with the bitmap... in a prctl() that's supposed to only be
dealing with the bitmap.

Yes, the bitmap address should have been masked, although it is checked for page
alignment (which has the same effect).  I will fix it.

Yu-cheng