Messages in this thread Patch in this message | | | Date | Wed, 13 Jan 2021 12:45:15 -0800 | Subject | [PATCH] KVM: x86: Add more protection against undefined behavior in rsvd_bits() | From | Sean Christopherson <> |
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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 <pbonzini@redhat.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- 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; -- 2.30.0.284.gd98b1dd5eaa7-goog
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