From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9F612C88E53 for ; Tue, 15 Sep 2026 07:04:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=TkOIvu8q2gHRPu8gLHr1j7FThQAssMDAlnryy77Ag5Q=; b=2dSgmxNrzpCXr1vlxf/iXk1kPi ng/yJnt0ENpv2E388Jsvgr0FSxkDHHGC+8rX5v+O4UX3/yvZ5FtZv1Nd9j5xEmHDpVxPfIt70dZH+ TY+IxA5fSBkAXJwebDNhmJM75bHgZNbPSt3Usk9R8u90krJirZzvHxE0WxrIZe4g0kRlICZHTxbNp cS1LUAZ72pJBT25kl+9y99oLnuG9XoLKYbLh+tpzYqKV0sQIrIa2f8CJAwx74KHU6nfFkoi+tM6Wl 1B24/9IFeQwWSkXtoQxdLlB8ZW9EMbv0Eh1xz6vPQJRGKGbdr1S3C64ITrOiiJvqpr9KB31J8DvAT j+fTpJ0A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6NDP-00000005Pl4-38kP; Tue, 15 Sep 2026 07:04:27 +0000 Received: from out-22.mta0.migadu.com ([2001:41d0:1004:224b::16] helo=mta0.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6NDN-00000005Pjq-2shh for linux-arm-kernel@lists.infradead.org; Tue, 15 Sep 2026 07:04:27 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=ANhxith82ULbv0/JaaJ8goUq0CxV3cuc4rjj5cuj3dU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1789455863; v=1; x=1790060663; b=p46XEyyi5VK6kYdJNj6dDh+yAg5PJ6zeWbO/NVYhYLMF4N41z2k4ANoHJzNnAdb1YNwH/1kz b/SpP/9onmTjkXf+PWhvslgIfxrgojUi4sbibhICmwlRT2UzDeTdXX4D/PYanWM7Mt3GKAMSJab H7e5yq0GgGvc7J/vMWuaurlo= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id 43fcf61e14ba3efe; Tue, 15 Sep 2026 07:04:23 +0000 X-Mizu-Trace-ID: 43fcf61e14ba3efe X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: catalin.marinas@arm.com, will@kernel.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, mark.rutland@arm.com, steven.price@arm.com, vdonnefort@google.com, qperret@google.com, tabba@google.com Subject: [PATCH v2 1/2] KVM: arm64: Validate the host vCPU's VM before reading it under pKVM Date: Tue, 15 Sep 2026 08:04:17 +0100 Message-Id: <20260915070418.3209779-2-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260915070418.3209779-1-fuad.tabba@linux.dev> References: <20260915070418.3209779-1-fuad.tabba@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260915_000425_862062_EFD0D428 X-CRM114-Status: GOOD ( 15.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On an MTE-capable host under pKVM, enter_exception64() reads the VM's MTE flag through vcpu->kvm, which for a host vCPU is a host-writable pointer nothing validates. The host can point it at any address in the hyp linear map and read back bit 1 of that word through PSR_TCO in the vCPU's CPSR, or panic the hypervisor with an unmapped one. Get the VM through a get/put pair around the read: a loaded vCPU's is the hyp VM, an unloaded host vCPU's is read once and pinned, and a pointer the host never shared leaves TCO clear. Fixes: ea7fc1bb1cd1b ("KVM: arm64: Introduce MTE VM feature") Reported-by: Sashiko Closes: https://lore.kernel.org/all/20260914070536.877D91F000FF@smtp.kernel.org/ Cc: stable@vger.kernel.org Signed-off-by: Fuad Tabba --- arch/arm64/kvm/hyp/exception.c | 5 ++- arch/arm64/kvm/hyp/include/hyp/adjust_pc.h | 18 ++++++++++ arch/arm64/kvm/hyp/nvhe/pkvm.c | 39 ++++++++++++++++++++++ 3 files changed, 61 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c index 754e2dc1df54a..6e60d890afa4a 100644 --- a/arch/arm64/kvm/hyp/exception.c +++ b/arch/arm64/kvm/hyp/exception.c @@ -70,6 +70,7 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode, enum exception_type type) { unsigned long sctlr, vbar, old, new, mode; + struct kvm *kvm; u64 exc_offset; mode = *vcpu_cpsr(vcpu) & (PSR_MODE_MASK | PSR_MODE32_BIT); @@ -109,8 +110,10 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode, new |= (old & PSR_C_BIT); new |= (old & PSR_V_BIT); - if (kvm_has_mte(kern_hyp_va(vcpu->kvm))) + kvm = vcpu_get_kvm(vcpu); + if (kvm && kvm_has_mte(kvm)) new |= PSR_TCO_BIT; + vcpu_put_kvm(vcpu, kvm); new |= (old & PSR_DIT_BIT); diff --git a/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h b/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h index 4fdfeabefeb43..a4fb04faa7d09 100644 --- a/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h +++ b/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h @@ -13,6 +13,24 @@ #include #include +/* + * Under pKVM a host vCPU's ->kvm is host-writable: the nVHE pair + * validates it. + */ +#ifdef __KVM_NVHE_HYPERVISOR__ +struct kvm *vcpu_get_kvm(struct kvm_vcpu *vcpu); +void vcpu_put_kvm(struct kvm_vcpu *vcpu, struct kvm *kvm); +#else +static inline struct kvm *vcpu_get_kvm(struct kvm_vcpu *vcpu) +{ + return vcpu->kvm; +} + +static inline void vcpu_put_kvm(struct kvm_vcpu *vcpu, struct kvm *kvm) +{ +} +#endif + static inline void kvm_skip_instr(struct kvm_vcpu *vcpu) { if (vcpu_mode_is_32bit(vcpu)) { diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 459bd9eb7e4bc..9bdc7a9b84b8c 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -11,6 +11,8 @@ #include +#include + #include #include #include @@ -304,6 +306,43 @@ struct pkvm_hyp_vcpu *pkvm_get_loaded_hyp_vcpu(void) } +static struct pkvm_hyp_vm *loaded_hyp_vm_of(struct kvm_vcpu *vcpu) +{ + struct pkvm_hyp_vcpu *hyp_vcpu = pkvm_get_loaded_hyp_vcpu(); + + if (hyp_vcpu && + (vcpu == &hyp_vcpu->vcpu || vcpu == hyp_vcpu->host_vcpu)) + return pkvm_hyp_vcpu_to_hyp_vm(hyp_vcpu); + + return NULL; +} + +/* An unloaded host vCPU's VM is mapped at EL2 only while pinned. */ +struct kvm *vcpu_get_kvm(struct kvm_vcpu *vcpu) +{ + struct pkvm_hyp_vm *hyp_vm; + struct kvm *kvm; + + if (!is_protected_kvm_enabled()) + return kern_hyp_va(vcpu->kvm); + + hyp_vm = loaded_hyp_vm_of(vcpu); + if (hyp_vm) + return &hyp_vm->kvm; + + kvm = kern_hyp_va(READ_ONCE(vcpu->kvm)); + if (hyp_pin_shared_mem(kvm, kvm + 1)) + return NULL; + + return kvm; +} + +void vcpu_put_kvm(struct kvm_vcpu *vcpu, struct kvm *kvm) +{ + if (kvm && is_protected_kvm_enabled() && !loaded_hyp_vm_of(vcpu)) + hyp_unpin_shared_mem(kvm, kvm + 1); +} + struct pkvm_hyp_vm *get_pkvm_hyp_vm(pkvm_handle_t handle) { struct pkvm_hyp_vm *hyp_vm; -- 2.39.5