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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 <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210113204515.3473079-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-01-13 12:45:15 -08:00 committed by Paolo Bonzini
parent a10f373ad3
commit eb79cd00ce
1 changed files with 8 additions and 1 deletions
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9
arch/x86/kvm/mmu.h
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@ -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;