From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794063098; b=dOI85ZJGb7fZpRjZ4NwkpLyZuHcvWC/gkXmqW1dFJoCUIEWVEKZNsH2A02mGZiJeMHQG t11evy6orJUtzrXUy6m4OcG4CjRwygeP+JrcOPbRVbO/MS8A72QJ/qwIPorDKlQt3EZ4g hx8NTtqApJ1o6TE944EYkaG3ZuaQwFwUJZKfIKDV3OiMd3VrH1mI49G6C3uCLRlKNwqya qSlRHybqpSWJ5N1htm+nwNlLwSfGQj/biqb3ottJkCK2LcAyey+XK7aXrGdgBUr6dVejj uzbyJexK4bNNvqaazLMFMGsUcpW5rSYJJjSlNBi7Cw9bofXI6kYXLVqxKBTyytCIFGA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794063098; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=ERje0JKsBworlz/Q6C6WG57HWTsTzvaSG2WHhErpqc0=; b=BnOtZViNzx2UJSJyjW9a+DELPbzKKJNB9VQk66XtC1WR+Tj4SBNTlq+nIsh9FRlfYKH9 Yic/TXiIDDJnjWvJ1IZqVsA+QBZdpP4b2T40Hj3EffgzdzePtU4goo5BlKZETu2JNb52d 3bIAlvrsY1ZMSK7X34Fhu1UWY+k1tS0a6rCJ7TB7M60eidpQE7R2OT3nwqUweG645dq9a NwPMlRWBWsCloJnhV0QYUyvYo7hhIajMEgrFSaDVD+yuHvansoO+YB7w98ZGtLM3Y5EBe ukbeE3khAbjDYSlAb5G1jZSnrwOT5U9BPXcMxLVRaoNXaIm8SDNrtIQtNXDyOcis/Rw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b="NZQ/vchW"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 42A60606D804; Sat, 7 Nov 2026 14:51:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=NZQ/vchW Received: by smtp.kernel.org (Postfix) with ESMTPSA id E688E1F008A1; Sat, 7 Nov 2026 14:51:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794063098; bh=ERje0JKsBworlz/Q6C6WG57HWTsTzvaSG2WHhErpqc0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NZQ/vchWMTCXPw2hLynKmWzVnxyDKvLXwxMe0tkWt+i0M6wUpRHAL6qxlQ7KRnyVE WUpBdBr+R2empglfVNoTH4+CQz1BdrWkW+YExG/p5o7XNKCxWTTaO6AAkSGKHqPPEz d7NKaRxlsCPsrYWpAQYTtuogfzq0UjzKndXReyPg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sashiko , Vincent Donnefort , Joey Gouly , Fuad Tabba , Marc Zyngier , Sasha Levin Subject: [PATCH 6.18 333/869] KVM: arm64: Validate the host vCPUs VM before reading it under pKVM Date: Sat, 7 Nov 2026 08:50:15 -0500 Message-ID: <20261107134903.708937762@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134852.069646174@linuxfoundation.org> References: <20261107134852.069646174@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Fuad Tabba [ Upstream commit cf533b4d3630b229d78ad55567c5db2f365052a2 ] 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/ Reviewed-by: Vincent Donnefort Reviewed-by: Joey Gouly Cc: stable@vger.kernel.org Signed-off-by: Fuad Tabba Link: https://patch.msgid.link/20261001135711.1640520-3-fuad.tabba@linux.dev Signed-off-by: Marc Zyngier Signed-off-by: Sasha Levin --- arch/arm64/kvm/hyp/exception.c | 5 ++- arch/arm64/kvm/hyp/include/hyp/adjust_pc.h | 28 ++++++++++++++++ arch/arm64/kvm/hyp/include/nvhe/pkvm.h | 2 ++ arch/arm64/kvm/hyp/nvhe/pkvm.c | 37 ++++++++++++++++++++++ 4 files changed, 71 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c index bef40ddb16dbc..c041142896e35 100644 --- a/arch/arm64/kvm/hyp/exception.c +++ b/arch/arm64/kvm/hyp/exception.c @@ -86,6 +86,7 @@ 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); @@ -125,8 +126,10 @@ 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..f55950ee2a7e4 100644 --- a/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h +++ b/arch/arm64/kvm/hyp/include/hyp/adjust_pc.h @@ -13,6 +13,34 @@ #include #include +#ifdef __KVM_NVHE_HYPERVISOR__ +#include + +/* Under pKVM a host vCPU's ->kvm is host-writable. */ +static inline struct kvm *vcpu_get_kvm(struct kvm_vcpu *vcpu) +{ + if (is_protected_kvm_enabled()) + return pkvm_vcpu_get_kvm(vcpu); + + return kern_hyp_va(vcpu->kvm); +} + +static inline void vcpu_put_kvm(struct kvm_vcpu *vcpu, struct kvm *kvm) +{ + if (is_protected_kvm_enabled()) + pkvm_vcpu_put_kvm(vcpu, 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/include/nvhe/pkvm.h b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h index 184ad7a399507..25b2f477bb5b2 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h +++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h @@ -79,6 +79,8 @@ struct pkvm_hyp_vcpu *pkvm_load_hyp_vcpu(pkvm_handle_t handle, unsigned int vcpu_idx); void pkvm_put_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu); struct pkvm_hyp_vcpu *pkvm_get_loaded_hyp_vcpu(void); +struct kvm *pkvm_vcpu_get_kvm(struct kvm_vcpu *vcpu); +void pkvm_vcpu_put_kvm(struct kvm_vcpu *vcpu, struct kvm *kvm); struct pkvm_hyp_vm *get_pkvm_hyp_vm(pkvm_handle_t handle); struct pkvm_hyp_vm *get_np_pkvm_hyp_vm(pkvm_handle_t handle); diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index bf0250806a781..136c4008b9363 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -306,6 +306,43 @@ struct pkvm_hyp_vcpu *pkvm_get_loaded_hyp_vcpu(void) } +static struct pkvm_hyp_vm *pkvm_get_loaded_hyp_vm(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; +} + +/* + * A loaded vCPU's VM is the hyp VM. An unloaded host vCPU's is mapped at + * EL2 only while pinned, so it's read once and pinned; the pin fails for + * memory the host isn't sharing. + */ +struct kvm *pkvm_vcpu_get_kvm(struct kvm_vcpu *vcpu) +{ + struct pkvm_hyp_vm *hyp_vm = pkvm_get_loaded_hyp_vm(vcpu); + struct kvm *kvm; + + 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 pkvm_vcpu_put_kvm(struct kvm_vcpu *vcpu, struct kvm *kvm) +{ + if (kvm && !pkvm_get_loaded_hyp_vm(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; -- 2.53.0