From eb79cd00ce25974c21f34f1eeb92a580ff572971 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 13 Jan 2021 12:45:15 -0800 Subject: 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: Paolo Bonzini Signed-off-by: Sean Christopherson Message-Id: <20210113204515.3473079-1-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.h | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 581925e476d6..261be1d2032b 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -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; -- cgit v1.2.3