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=1794049295; b=o8MuEyXVwKQn2p/7C4ssZuZrMUfuBu3h7tqZqs71yVoyA3H7k0th0Ab0+QlOmf/m8CTF yKJeINrz1RFDw1n6qfkhONBGsELOqwDH0xDAnobvptwz5pPuTdtA3I+GaQa+ctgAiKTfz 9cSaFVnXzC/YiiA/vJaAVtYpB+Kj0g0PeRZrdh9vLSJv7ZMH+oAcBg3n6JQ9/G7yu3WW9 OXKAuJ9Aa4C3mxTEf7XT+jfMfyZj+WD4wwP/BRnXVc9awpeY/Cty/WJrjjABSVyY6sfB/ gf3gmWPxs8UGxoAu8GvQ5zrlPvnDnfLWZhxQJNNsAEMXJO1pYD1B0/jSyLxCEACwAgg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794049295; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=qXAmKezvQiG+VgIgxQi/VgWuJt4PPRUP5kXhoMHZOQs=; b=l9jHxirh7zdBWHwS/LP5jIg2QyvA7jMBotgK7VSeL5uAuaZRdjORCUIdJaUGfRy3uOZ4 Upc9VnJIkKpQ6icLmswtFwoL0UIl4PyPrTND3HlmhJ+jQRtoJ0XuyLV5jDr4i1ee8SRy2 JXWsrqsljCobqWZz3bLh4pG5xdeckl1nPNCYfamvxA4h+z5BdjZ2EM/ap5dTCzlAvTJmN 1o6GG8jYkF8sNBLrClSucuL/t6BVUnpj+T0ms0v9ap0Fn9J3S0OHkl+9IxdmTAeQrMx9m oPxzzuNBWZwwl/E5xxAofNNOltLjK+P0Zc7X2zDEvi4Iofogyb2Jz7Hivp9gLQz1OXg== 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=jsikOgwf; 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 9C352606A333 for ; Sat, 7 Nov 2026 11:01:35 +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=jsikOgwf Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFACC1F008A7; Sat, 7 Nov 2026 11:01:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794049295; bh=qXAmKezvQiG+VgIgxQi/VgWuJt4PPRUP5kXhoMHZOQs=; h=From:To:Cc:Subject:Date; b=jsikOgwf9IaPtm5lVkaY9bqaq3bRsp/L7jzps7WMbMvNzINYb5TAmCV7wU1Agrhor ZyMqvuVyiHKnx5jY69ftEBnld6k9XjSlo/1zVbWc3lwl0EgJiMd8wIgqYoalwSNTul 4YBzIyaijz7p4iS1GPORF6bohrr7Zo62kARt1w42/7i4mQnuKWEAwGc2kBGIEOTxYW 8MJRoXQVrBEk0j7AQjNFVqP4aC5YmWXWgTrDJwRMj85g4Ty2npuksS/aZ/2e8fvOyV YdP1cqywqS/43JEUruXHx5/f+zfa4LvonNvCjRP0CoHmg7CBU9PlDRCqXUpCeZ1fy7 FvQ1P6PcaCHiQ== From: Sasha Levin To: fuad.tabba@linux.dev, sashiko-bot@kernel.org, vdonnefort@google.com, joey.gouly@arm.com, maz@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] KVM: arm64: Validate the host vCPU's VM before reading it under pKVM" failed to apply to 5.15-stable tree Date: Sat, 7 Nov 2026 06:01:33 -0500 Message-ID: <20261107060133-failed-5.15-cf533b4d3630@kernel.org> X-Mailer: git-send-email 2.53.0 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x cf533b4d3630b229d78ad55567c5db2f365052a2 # git commit -s git send-email --to '' --in-reply-to '20261107060133-failed-5.15-cf533b4d3630@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From cf533b4d3630b229d78ad55567c5db2f365052a2 Mon Sep 17 00:00:00 2001 From: Fuad Tabba Date: Thu, 1 Oct 2026 14:56:55 +0100 Subject: [PATCH] KVM: arm64: Validate the host vCPU's VM before reading it under pKVM 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 --- 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 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..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 c904647d2f760..5ddb407149667 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h +++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h @@ -83,6 +83,8 @@ 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 459bd9eb7e4bc..0e90de74778cf 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -304,6 +304,43 @@ 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