linux-kernel - [PATCH] KVM: x86/mmu: Fix a benign Bitwise vs. Logical OR mixup

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200108001859.25254-1-sean.j.christopherson@intel.com>
Date:   Tue,  7 Jan 2020 16:18:59 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86/mmu: Fix a benign Bitwise vs. Logical OR mixup

Use a Logical OR in __is_rsvd_bits_set() to combine the two reserved bit
checks, which are obviously intended to be logical statements.  Switching
to a Logical OR is functionally a nop, but allows the compiler to better
optimize the checks.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/mmu/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7269130ea5e2..72e845709027 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3970,7 +3970,7 @@ __is_rsvd_bits_set(struct rsvd_bits_validate *rsvd_check, u64 pte, int level)
 {
 	int bit7 = (pte >> 7) & 1, low6 = pte & 0x3f;
 
-	return (pte & rsvd_check->rsvd_bits_mask[bit7][level-1]) |
+	return (pte & rsvd_check->rsvd_bits_mask[bit7][level-1]) ||
 		((rsvd_check->bad_mt_xwr & (1ull << low6)) != 0);
 }
 
-- 
2.24.1