Re: [PATCH] KVM: x86: fix a typo in __try_cmpxchg_user that caused cmpxchg to be not atomic

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, May 12, 2022, Vitaly Kuznetsov wrote:
> Maxim Levitsky <mlevitsk@xxxxxxxxxx> writes:
> 
> > Fixes: 1c2361f667f36 ("KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses")
> > Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> > ---
> >  arch/x86/kvm/x86.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > Yes, this is the root cause of the TDP mmu leak I was doing debug of in the last week.
> > Non working cmpxchg on which TDP mmu relies makes it install two differnt shadow pages
> > under same spte.

Ewww, as in running a buggy L0 resulted in a CMPXCHG going sideways in L1?  That's
awful.  My apologies :-(

> In case the fix is not squashed with 1c2361f667f36, the above should
> really go before '---'.
> 
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 8ee8c91fa7625..79cabd3d97d22 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -7329,7 +7329,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> >  		goto emul_write;
> >  
> >  	hva = kvm_vcpu_gfn_to_hva(vcpu, gpa_to_gfn(gpa));
> > -	if (kvm_is_error_hva(addr))
> > +	if (kvm_is_error_hva(hva))
> 
> Looks like a typo indeed, so
> 
> Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>

Yep, if this doesn't get squashed

Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>



[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]

  Powered by Linux