linux-kernel - [PATCH 06/10] KVM: Fix last_boosted

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

Message-ID: <20251110033232.12538-7-kernellwp@gmail.com>
Date: Mon, 10 Nov 2025 11:32:27 +0800
From: Wanpeng Li <kernellwp@...il.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	Wanpeng Li <wanpengli@...cent.com>
Subject: [PATCH 06/10] KVM: Fix last_boosted_vcpu index assignment bug

From: Wanpeng Li <wanpengli@...cent.com>

From: Wanpeng Li <wanpengli@...cent.com>

In kvm_vcpu_on_spin(), the loop counter 'i' is incorrectly written to
last_boosted_vcpu instead of the actual vCPU index 'idx'. This causes
last_boosted_vcpu to store the loop iteration count rather than the
vCPU index, leading to incorrect round-robin behavior in subsequent
directed yield operations.

Fix this by using 'idx' instead of 'i' in the assignment.

Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 virt/kvm/kvm_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b7a0ae2a7b20..cde1eddbaa91 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4026,7 +4026,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
 
 		yielded = kvm_vcpu_yield_to(vcpu);
 		if (yielded > 0) {
-			WRITE_ONCE(kvm->last_boosted_vcpu, i);
+			WRITE_ONCE(kvm->last_boosted_vcpu, idx);
 			break;
 		} else if (yielded < 0 && !--try) {
 			break;
-- 
2.43.0