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SubjectRe: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function
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On Fri, 2019-06-07 at 12:03 -0700, Dave Hansen wrote:
> On 6/6/19 1:09 PM, Yu-cheng Yu wrote:
> > + 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

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