From 7795afa0d7a907df392483efe9a38b4f875169f7 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 22 Dec 2020 05:20:43 -0500 Subject: [PATCH] KVM: x86: fix shift out of bounds reported by UBSAN commit 2f80d502d627f30257ba7e3655e71c373b7d1a5a upstream. Since we know that e >= s, we can reassociate the left shift, changing the shifted number from 1 to 2 in exchange for decreasing the right hand side by 1. Reported-by: syzbot+e87846c48bf72bc85311@syzkaller.appspotmail.com Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/mmu.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 6f2208cf30df..ea9945a05b83 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -48,7 +48,7 @@ static inline u64 rsvd_bits(int s, int e) if (e < s) return 0; - return ((1ULL << (e - s + 1)) - 1) << s; + return ((2ULL << (e - s)) - 1) << s; } void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask, u64 mmio_value, u64 access_mask);