KVM: x86: fix shift out of bounds reported by UBSAN

stable inclusion
from stable-5.10.7
commit 563135ec664ffb80a2297e94d618b04b228a1262
bugzilla: 47429

--------------------------------

commit 2f80d502 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: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

arch/x86/kvm/mmu.h

@@ -49,7 +49,7 @@ 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_value, u64 access_mask);