Commit eb79cd00 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86: Add more protection against undefined behavior in rsvd_bits() 



Add compile-time asserts in rsvd_bits() to guard against KVM passing in
garbage hardcoded values, and cap the upper bound at '63' for dynamic
values to prevent generating a mask that would overflow a u64.

Suggested-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20210113204515.3473079-1-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a10f373a

arch/x86/kvm/mmu.h

+8 −1
Original line number Diff line number Diff line
@@ -44,8 +44,15 @@ 
#define PT32_ROOT_LEVEL 2

#define PT32E_ROOT_LEVEL 3



static inline u64 rsvd_bits(int s, int e)

static __always_inline u64 rsvd_bits(int s, int e)

{

	BUILD_BUG_ON(__builtin_constant_p(e) && __builtin_constant_p(s) && e < s);



	if (__builtin_constant_p(e))

		BUILD_BUG_ON(e > 63);

	else

		e &= 63;



	if (e < s)

		return 0;