From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3475E48BD20; Tue, 1 Sep 2026 17:29:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788283775; cv=none; b=R0dL9xsuxjthelv5nFajAaJIzXj65oK8AOSRir4bwcmFqdOK9MljdPLjGOJtSGxCr/w9yoAB3DZBzSkJEk9EZs2y15JZbXdiMuLWyb2Nvpz0iMQYh/55TUAEtKyJkOgWeK9Xf1fU3AFTAcDSW/QABqAjOiyftXq/ICrzh3Ou1gM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788283775; c=relaxed/simple; bh=hIJQVO5FZNvdm0cmp7KFRCyJsyxlcDY2tLzeNko9CCQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=qGFlyVY1/pjCtreMn9jf0cvDRqDD2UjNpg0npmDBiSd+I3xbTZZyM6JACoYkN85x+OzKR5GvMVvZE0P18dpDC1FyMmeWgF3EBmJYidWHw7YAZpGmMSf9lbqlUGJZiktf9P+jYW4JxC2WcD0hRyCe8JxMhSnoyecEIc0GqZtZ1D8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KtkmMZlm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KtkmMZlm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99B5A1F00A3E; Tue, 1 Sep 2026 17:29:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788283773; bh=EVyNmPZk8xroeMlfEyBXTtkBWQBzLnb7LaqjL0r2gKY=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=KtkmMZlm7pdlaVD2POunK3BmTzCzGjOiaFm/Kk5cnszKSNphKUepiWoDULW+vEQ4e PkjA+G/48biGxGdgisfCpcPRNoQ8Y80A/rsMwZuWnp7VZpxJl2VpvZSYRRZEybRzV2 f6YkrWLFdyaVYExTK3p6FZ3D7sfYP8IKivZlOWjROJikuGF5gYFe63U1ozizDYXKdp NqJ7WjaghELgFfkXEBRtYIHm3e4fGjPBvfbzXYLt6qTSaazHFBMPuuCk1lKtjHKocj 5O9rMzhMZfGs/SR18+lQWbLbrxGHysTvtkVVtc3qjbg4GnP6wWUlt6h7HWjZO3fE9M b8yJZW0GPf1+Q== From: "Lorenzo Stoakes (ARM)" Date: Tue, 01 Sep 2026 18:29:00 +0100 Subject: [PATCH v3 2/2] KVM: arm64: nv: Fix null ptr deref on nested wp/unmap, teardown race Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260901-kvm-arm-nested-virt-fix-v3-2-b154676f7e4c@kernel.org> References: <20260901-kvm-arm-nested-virt-fix-v3-0-b154676f7e4c@kernel.org> In-Reply-To: <20260901-kvm-arm-nested-virt-fix-v3-0-b154676f7e4c@kernel.org> To: Marc Zyngier , Oliver Upton , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Christoffer Dall , Fuad Tabba Cc: Wei-Lin Chang , Yao Yuan , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, "Lorenzo Stoakes (ARM)" , stable@vger.kernel.org X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=3208; i=ljs@kernel.org; h=from:subject:message-id; bh=hIJQVO5FZNvdm0cmp7KFRCyJsyxlcDY2tLzeNko9CCQ=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLKmcxf5Mv/I4XDw3rh/n/efK/dZIqJTN9c/tGDv9rXML 3cxX1XWUcrCIMbFICumyPL8i/j+IJGweZ0X/N1g5rAygQxh4OIUgIkcE2P4X9PZksZ/X+c9709b aSaLHXf2T3++2tr3fRr3kuf+xSLWzgz/w/+1l19Y++Pz/7g7P5b4Bs2cyyk7m/W6akOIMTdntI8 fDwA= X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 Commit 7270cc9157f4 ("KVM: arm64: nv: Handle VNCR_EL2 invalidation from MMU notifiers") introduced VNCR_EL2 invalidation in both kvm_nested_s2_unmap() and kvm_nested_s2_wp(). However at the point of this being performed concurrent stage 2 teardown of a nested guest can cause kvm->arch.mmu.pgt to be set to NULL. This happens in kvm_flush_shadow_all() -> kvm_arch_flush_shadow_all() -> kvm_free_stage2_pgd() and is performed under the kvm->mmu_lock. Commit ec14c272408a ("KVM: arm64: nv: Unmap/flush shadow stage 2 page tables") introduced the teardown of the entire nested MMU range, which then invokes stage2_apply_range() with resched=true: mmu_notifier_invalidate_range_start() -> ... -> kvm_mmu_notifier_invalidate_range_start() -> kvm_mmu_unmap_gfn_range() -> kvm_unmap_gfn_range() -> kvm_nested_s2_unmap() -> kvm_stage2_unmap_range() -> __unmap_stage2_range() -> stage2_apply_range() This means that stage2_apply_range() can drop the kvm->mmu_lock and thus concurrent progress can be made in lockstep with kvm_arch_flush_shadow_all(). If kvm_arch_flush_shadow_all() advances ahead of stage2_apply_range() and completes its operation it guarantees a NULL pointer deref. Since kvm_free_stage2_pgd() is performed under the kvm->mmu_lock this will either be observed NULL or not and serialised against kvm_free_stage2_pgd(). Resolve the issue by abstracting the invalidation to a new function, kvm_invalidate_vncr_ipa_all(), and check that the pgt is non-NULL before dereferencing it. Fixes: 7270cc9157f4 ("KVM: arm64: nv: Handle VNCR_EL2 invalidation from MMU notifiers") Cc: stable@vger.kernel.org Reviewed-by: Marc Zyngier Signed-off-by: Lorenzo Stoakes (ARM) --- arch/arm64/kvm/nested.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 17123f0b6dab..f69722e1592a 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1260,6 +1260,17 @@ void kvm_handle_s1e2_tlbi(struct kvm_vcpu *vcpu, u32 inst, u64 val) invalidate_vncr_va(vcpu->kvm, &scope); } +static void kvm_invalidate_vncr_ipa_all(struct kvm *kvm) +{ + struct kvm_pgtable *pgt = kvm->arch.mmu.pgt; + + lockdep_assert_held_write(&kvm->mmu_lock); + + /* if the mmu lock was dropped, pgt teardown may have raced. */ + if (pgt) + kvm_invalidate_vncr_ipa(kvm, 0, BIT(pgt->ia_bits)); +} + void kvm_nested_s2_wp(struct kvm *kvm) { int i; @@ -1276,7 +1287,7 @@ void kvm_nested_s2_wp(struct kvm *kvm) kvm_stage2_wp_range(mmu, 0, kvm_phys_size(mmu)); } - kvm_invalidate_vncr_ipa(kvm, 0, BIT(kvm->arch.mmu.pgt->ia_bits)); + kvm_invalidate_vncr_ipa_all(kvm); } void kvm_nested_s2_unmap(struct kvm *kvm, bool may_block) @@ -1295,7 +1306,7 @@ void kvm_nested_s2_unmap(struct kvm *kvm, bool may_block) kvm_stage2_unmap_range(mmu, 0, kvm_phys_size(mmu), may_block); } - kvm_invalidate_vncr_ipa(kvm, 0, BIT(kvm->arch.mmu.pgt->ia_bits)); + kvm_invalidate_vncr_ipa_all(kvm); } void kvm_nested_s2_flush(struct kvm *kvm) -- 2.55.0