From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-46.mta0.migadu.com [91.218.175.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2DFA835C6A9 for ; Thu, 13 Aug 2026 23:25:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786663557; cv=none; b=Nq4rlL8hulxw1Ro6JcNC0EP5g/OKHmSBGqKR6S7RpyzDrM+gtRVWHwDktw0Wl1Ua8YKrKhPlr1x37ZVt65KgRGaBLfPsDgW0ryOv5ddiBRSL54qHjpFvPPSX816LnLkLbPyRv/rz3tiYmNUfH1cKHsfcyqb4ukGVpeyFXGALf5s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786663557; c=relaxed/simple; bh=Enf+YsjOMprKXPN86ka3rREmGOuZZK8yt2Up1k9KAKw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=dgy0jvBkTu/x9ZeDrPd6kGueV0KBicnXHLW/86eZplF9+0h0352T4zGrDc7e97QYipA91diuFrogoe4gANkwuCtYrIpDFpWtYP5OW184p1tKxLKc1UNYboKoJ8g1Tx6K+xToJBkLcxg4usAQl1ZXCdFzRO+k96fpsQuZoXmxxR4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=uQ04qzyE; arc=none smtp.client-ip=91.218.175.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="uQ04qzyE" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=Enf+YsjOMprKXPN86ka3rREmGOuZZK8yt2Up1k9KAKw=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1786663553; v=1; x=1787268353; b=uQ04qzyEQJ/HBImk1gyaqt1tYKSL3EyOot8lJchCEssS6xSghXNTRDk+qPtG0xX71QJrM7zi uvjUyTZU87aRByHDI7Tu/mB4Dk11lJZK3f1CU/LMA+UoahNWV2YOizMFpSFBeKSjpYbEBfPFXu+ +rNyYiVrwdLSCj8mFQUrclzI= X-Envelope-To: linux-kernel@vger.kernel.org Received: from ctao-book.. (111.162.215.50) by smtp.migadu.com with ESMTPS id afc9b2f00fdf83c6; Thu, 13 Aug 2026 23:25:53 +0000 X-Migadu-Flow: FLOW_OUT From: Tao Cui To: maobibo@loongson.cn Cc: zhaotianrui@loongson.cn, chenhuacai@kernel.org, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, cui.tao@linux.dev, Tao Cui Subject: [PATCH v2] LoongArch: KVM: Fix TOCTOU race on pv_features Date: Fri, 14 Aug 2026 07:25:42 +0800 Message-ID: <20260813232542.2098930-1-cui.tao@linux.dev> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Tao Cui The check-then-set on kvm->arch.pv_features in kvm_loongarch_cpucfg_set_attr() is lockless, so two vCPUs can race past the validation and set different values. Add a spinlock to serialize it. Signed-off-by: Tao Cui --- Changes in v2: use a spinlock instead of a cmpxchg loop (Bibo Mao). Link: https://lore.kernel.org/all/20260810081321.157258-1-cui.tao@linux.dev/ arch/loongarch/include/asm/kvm_host.h | 2 ++ arch/loongarch/kvm/vcpu.c | 6 +++++- arch/loongarch/kvm/vm.c | 1 + 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h index 23cfbecebbd7..cdbbd90e0584 100644 --- a/arch/loongarch/include/asm/kvm_host.h +++ b/arch/loongarch/include/asm/kvm_host.h @@ -128,6 +128,8 @@ struct kvm_arch { struct kvm_phyid_map *phyid_map; /* Enabled PV features */ unsigned long pv_features; + /* Serializes pv_features updates */ + spinlock_t pv_features_lock; /* Supported KVM features */ unsigned long kvm_features; diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c index 20c207d80e31..551ed39b2d1f 100644 --- a/arch/loongarch/kvm/vcpu.c +++ b/arch/loongarch/kvm/vcpu.c @@ -1165,10 +1165,14 @@ static int kvm_loongarch_cpucfg_set_attr(struct kvm_vcpu *vcpu, return -EINVAL; /* All vCPUs need set the same PV features */ + spin_lock(&kvm->arch.pv_features_lock); if ((kvm->arch.pv_features & LOONGARCH_PV_FEAT_UPDATED) - && ((kvm->arch.pv_features & valid) != val)) + && ((kvm->arch.pv_features & valid) != val)) { + spin_unlock(&kvm->arch.pv_features_lock); return -EINVAL; + } kvm->arch.pv_features = val | LOONGARCH_PV_FEAT_UPDATED; + spin_unlock(&kvm->arch.pv_features_lock); return 0; default: return -ENXIO; diff --git a/arch/loongarch/kvm/vm.c b/arch/loongarch/kvm/vm.c index 1317c718f896..b984cc54f305 100644 --- a/arch/loongarch/kvm/vm.c +++ b/arch/loongarch/kvm/vm.c @@ -76,6 +76,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) return -ENOMEM; } spin_lock_init(&kvm->arch.phyid_map_lock); + spin_lock_init(&kvm->arch.pv_features_lock); kvm_init_vmcs(kvm); kvm_vm_init_features(kvm); -- 2.43.0