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=1794363786; b=SPEZj0qSnqmcgQoq73lx5Nixl6SNdicCZAqHSQHaoA24xjBbRGTct0BE5j9H2IoL12ry w4uaWPDF9BI1NRabKSUckLw5tkg/T06zIgz9d108UqjIqY0mMWpy98OUo7T2PR3zqMdYu KKK3Rc9iWZHawb4cda1+9/ySacSX1Bp94DFVfVGbLe26EOfZENrMAwvSykNsBsawU7rKu Iz6CasWksrey0nswbxR6mKm3lo8agEyI+X49vlmzAgAKaCWsO17r2mranb1QEr64Z7eqi zv7sWyUTeVICC0CttPuSA9SPk4TcflCys2CnZAB3x5puTRZkdZOYUt8sv+p0QEkQA/g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794363786; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=RQBfIu1xOwEYElu8JsmkRMDUzf9z5r+TFaUJBC5jnrU=; b=aDJeP3dkcxWwEzQaRZwoLRyCjasykDEqBm832g2eSVBE/sI9vK8R9LJ1VKmL3bSoksts kzumuzUSgylKmKP5xnspqaVEPmC/hGHsh32Hke49wF5glHTwuiuAYmwVQHxc+qXmXHcTP zG+huqtH34MLKYfO+12EC+0J6Raqz/8lvE72n0fdF+brSaxHY+Ecmdmh5CIeL4XHEvzOu rHXnmEaUWKkhm5NUSUaJesApkdEt0HjvNM1JCXhJfeRM9VJ238ZJMxSpZKp2Gu7sUqG3s 1lVLfbeO/b68Ak4ioDtrcpYR2bdOwSxugeHa9mkzkT2E+IpxLIu346n3+77xUfIjAFg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=an80zKMP; 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 52468606A31C for ; Wed, 11 Nov 2026 02:23:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=an80zKMP Received: by smtp.kernel.org (Postfix) with ESMTPSA id 27A0E1F0089F; Wed, 11 Nov 2026 02:23:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794363785; bh=RQBfIu1xOwEYElu8JsmkRMDUzf9z5r+TFaUJBC5jnrU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=an80zKMPopcSBwPuHJsthLJmKhTpZHNMZYoJWsrwOyKr8UZH9KZirOMQBJbDVhRKJ vXZ5YeVzBq9XrKIJL7GPSpK54DvROQn6OjpVboVX2rLZJ/ENgvscd7Syj1HRPkbmFx sNsUaGmTf3jCMJvC5u/CxCyBadV6JqRZNyOjoroJL4O8scU8gpQa2J8iBUs87iBz2e 1LgnwliTI/LJ5wbBEEduvJW59TRzVarXbLAEXWgeltLNgOOL6div68EEGz9OzfodUF dFr6yYxWwvZMSrNZBLfo0cp6HpGeO1copYGNjMi8jb/7pWjhTcWBKs1TnRssjOokoa Y1I2deFcc4GAQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Fuad Tabba , Sashiko , Vincent Donnefort , Joey Gouly , Marc Zyngier , Sasha Levin Subject: [PATCH 6.6.y] KVM: arm64: Validate the host vCPU's VM before reading it under pKVM Date: Tue, 10 Nov 2026 21:23:03 -0500 Message-ID: <20261111022039.591632-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107053113-failed-6.6-cf533b4d3630@kernel.org> References: <20261107053113-failed-6.6-cf533b4d3630@kernel.org> 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 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 [ sashal: replaced unavailable pkvm_get_loaded_hyp_vcpu() with a NULL-checked lookup through host_ctxt->__hyp_running_vcpu. ] 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 | 43 ++++++++++++++++++++++ 4 files changed, 77 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c index 424a5107cddb5..e20979138305a 100644 --- a/arch/arm64/kvm/hyp/exception.c +++ b/arch/arm64/kvm/hyp/exception.c @@ -92,6 +92,7 @@ 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); @@ -131,8 +132,10 @@ 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 82b3d62538a61..d8efb924d57fd 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h +++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h @@ -64,5 +64,7 @@ int __pkvm_teardown_vm(pkvm_handle_t handle); 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 kvm *pkvm_vcpu_get_kvm(struct kvm_vcpu *vcpu); +void pkvm_vcpu_put_kvm(struct kvm_vcpu *vcpu, struct kvm *kvm); #endif /* __ARM64_KVM_NVHE_PKVM_H__ */ diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index fd3e0b2891c60..471cef3e29df6 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -258,6 +258,49 @@ void pkvm_put_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) hyp_spin_unlock(&vm_table_lock); } +static struct pkvm_hyp_vm *pkvm_get_loaded_hyp_vm(struct kvm_vcpu *vcpu) +{ + struct kvm_cpu_context *host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt; + struct kvm_vcpu *running_vcpu = host_ctxt->__hyp_running_vcpu; + struct pkvm_hyp_vcpu *hyp_vcpu; + + if (!running_vcpu) + return NULL; + + hyp_vcpu = container_of(running_vcpu, struct pkvm_hyp_vcpu, vcpu); + + if (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); +} + static void unpin_host_vcpu(struct kvm_vcpu *host_vcpu) { if (host_vcpu) -- 2.53.0