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 9197551DDF3; Wed, 30 Sep 2026 18:40:59 +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=1790793661; cv=none; b=g+tl8M73OFq5rqjTHfT+PK1CXt3Fw3KiZuzHf2oHmzvMeqb43jviu5GiXJ5YUfvyvY34Hemi2QBkpTGp7nN9vMQTBvWIjhIQ6wKf2PTRgWbQc+GFYamH1E9frqpfEIcmOsfkfF3tc3OP6z9caP6iZsQ3fx76ZTraVPVip/RcStg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790793661; c=relaxed/simple; bh=tf8ivjuvLwLhcunLQ2hkZByt79PbFWGhwwQzI5pdwhU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ccasQTmpwz2MY6KtLxsUJhOZoGv6jtnnxKwwv7YENvaBOOnnn0E+m0y0XVawHMo4TUj+LQmJxpdwH05sNCBz3SRcQJn7U9LFHViFhQyqU586SA3X8nxCM7CGPYW1be4EbC6oAyeTOsX8dSl9WQ3oCbISyH4D7B9dAZoAeMfWIn0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LaLJ4vV3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="LaLJ4vV3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AD52F1F000FF; Wed, 30 Sep 2026 18:40:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790793659; bh=37HgPgTXzAqYeaL2yKF1MPobW2qKxzGc7fiTZhu3kfE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LaLJ4vV3T3Hi7YBssIur2uAe4vOdsMBlxR6ufgxrjKI7nMkIMg22PqxmHUkInWTSG Jdb4bCiViY9af6LSc4kvyWovc1ofsI2/YAXfFFJQV7vty6ZpmY1hZ/kKxM3v6oXWRn cX3j9BBY2logKJP+dtlAJ7R7ruT2zFcvxW1Z1PVM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Marc Zyngier , "Lorenzo Stoakes (ARM)" , Jonathan Davies , Oliver Upton Subject: [PATCH 6.18 316/395] KVM: arm64: nv: Fix null ptr deref on nested wp/unmap, teardown race Date: Wed, 30 Sep 2026 17:29:38 +0200 Message-ID: <20260930152347.512032203@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152340.591469096@linuxfoundation.org> References: <20260930152340.591469096@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lorenzo Stoakes (ARM) commit 4c74e233cdedd11592775fae2a6243e67ca3f891 upstream. 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) Tested-by: Jonathan Davies Link: https://patch.msgid.link/20260901-kvm-arm-nested-virt-fix-v3-2-b154676f7e4c@kernel.org Signed-off-by: Oliver Upton Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kvm/nested.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1129,6 +1129,17 @@ void kvm_handle_s1e2_tlbi(struct kvm_vcp 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; @@ -1142,7 +1153,7 @@ 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) @@ -1158,7 +1169,7 @@ void kvm_nested_s2_unmap(struct kvm *kvm 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)