From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 2B54143F080; Wed, 16 Sep 2026 23:04:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789599900; cv=none; b=tnTGnFVj636/R6hdcLhxV2Tfnd+ljy6KKmLZnaHftPFmNl9k7zx473WsiyFG0spQEhvxFQEXq2TIDaRh+Oy4VklG5BPYmkIynsVzlv7O8mN5qQ8qqxPG84k77Glkcq5YYp6kd3SYiHvxRzpx/HF3qaXO7Se7Jtal9sB9qnCp89I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789599900; c=relaxed/simple; bh=vAFrHWJhmqJ9JZijWWOPIIzgx1x4jbVSOAfXEjggRyE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Y6+WL6DcoLGY4OpG2KpsYX7hZbPm1rJBnL13iSa69QhdOIZArxC3KJqHb/lviTOWYoWiTmQp+xH7OTG8X9rEzQ1yAnq5paFNZPHnZufBPYNZA4ph8qUwMeatuHpEAfIqUqtZnsHvTlY3z2aNcc6SBkPgDQtcM+n72E2jMHtzLYQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=kA7LM8H1; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="kA7LM8H1" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ED9C11477; Wed, 16 Sep 2026 16:04:53 -0700 (PDT) Received: from workstation-e142269.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 56C573F7B4; Wed, 16 Sep 2026 16:04:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1789599897; bh=vAFrHWJhmqJ9JZijWWOPIIzgx1x4jbVSOAfXEjggRyE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kA7LM8H1OpkdNGp2irBjX5CsQBDrt+cJIsSqMhgERYavYzt5474QgreduJ9Yrae9i ic/a6FT9wL8gzGrWyQrZYJkFy4lOkJ5yivHl4HSrFhd7MGtQ8xNm1kqztMzNgpArmF 36ykGbIFADQGlUdkl9JnQxNcAuBU7Vg/A/Esv/ZM= From: Wei-Lin Chang To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Marc Zyngier , Oliver Upton , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Vincent Donnefort , Sebastian Ene , Itaru Kitayama , Wei-Lin Chang , Sashiko AI , stable@vger.kernel.org Subject: [PATCH v3 1/2] KVM: arm64: ptdump: Check the page tables aren't freed when accessing Date: Thu, 17 Sep 2026 00:03:36 +0100 Message-ID: <20260916230337.4162485-2-weilin.chang@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260916230337.4162485-1-weilin.chang@arm.com> References: <20260916230337.4162485-1-weilin.chang@arm.com> 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: 8bit An open debugfs file keeps the KVM structure alive, but does not prevent mmu notifier release from freeing the stage-2 page tables when the VMM’s address space is torn down. Therefore page tables belonging to the mmus could have been freed when a thread opens or reads the ptdump files. Take the mmu_lock and check mmu->pgt is still alive before accessing the page tables. Also for the ipa_range file and stage2_levels file, switch from keeping the pointer to the page tables to keeping the pointer to the mmu. Fixes: 7c4f73548ed1 ("KVM: arm64: Register ptdump with debugfs on guest creation") Reported-by: Sashiko AI Closes: https://lore.kernel.org/kvmarm/20260623144054.B91D21F000E9@smtp.kernel.org/ Signed-off-by: Wei-Lin Chang Cc: stable@vger.kernel.org --- arch/arm64/kvm/ptdump.c | 43 +++++++++++++++++++++++++++++++---------- 1 file changed, 33 insertions(+), 10 deletions(-) diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c index 69899797dbad..4ead856c181a 100644 --- a/arch/arm64/kvm/ptdump.c +++ b/arch/arm64/kvm/ptdump.c @@ -115,15 +115,28 @@ static int kvm_ptdump_build_levels(struct ptdump_pg_level *level, u32 start_lvl) static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm_s2_mmu *mmu) { + struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu); struct kvm_ptdump_guest_state *st; - struct kvm_pgtable *pgtable = mmu->pgt; + s8 start_level; int ret; + /* + * We only need the pgt start level to initialize the ptdump, get it + * while holding the mmu_lock. It's fine if the pgt gets freed + * afterwards, we'll check again when doing the actual dump. + */ + scoped_guard(write_lock, &kvm->mmu_lock) { + if (mmu->pgt) + start_level = mmu->pgt->start_level; + else + return ERR_PTR(-ENOENT); + } + st = kzalloc_obj(struct kvm_ptdump_guest_state, GFP_KERNEL_ACCOUNT); if (!st) return ERR_PTR(-ENOMEM); - ret = kvm_ptdump_build_levels(&st->level[0], pgtable->start_level); + ret = kvm_ptdump_build_levels(&st->level[0], start_level); if (ret) { kfree(st); return ERR_PTR(ret); @@ -149,6 +162,9 @@ static int kvm_ptdump_guest_show(struct seq_file *m, void *unused) }; guard(write_lock)(&kvm->mmu_lock); + if (!mmu->pgt) + return 0; + st->parser_state = (struct ptdump_pg_state) { .marker = &st->ipa_marker[0], .end_address = BIT(mmu->pgt->ia_bits), @@ -211,17 +227,27 @@ static const struct file_operations kvm_ptdump_guest_fops = { static int kvm_pgtable_range_show(struct seq_file *m, void *unused) { - struct kvm_pgtable *pgtable = m->private; + struct kvm_s2_mmu *mmu = m->private; + struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu); + + guard(write_lock)(&kvm->mmu_lock); + + if (mmu->pgt) + seq_printf(m, "%2u\n", mmu->pgt->ia_bits); - seq_printf(m, "%2u\n", pgtable->ia_bits); return 0; } static int kvm_pgtable_levels_show(struct seq_file *m, void *unused) { - struct kvm_pgtable *pgtable = m->private; + struct kvm_s2_mmu *mmu = m->private; + struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu); + + guard(write_lock)(&kvm->mmu_lock); + + if (mmu->pgt) + seq_printf(m, "%1d\n", KVM_PGTABLE_MAX_LEVELS - mmu->pgt->start_level); - seq_printf(m, "%1d\n", KVM_PGTABLE_MAX_LEVELS - pgtable->start_level); return 0; } @@ -230,15 +256,12 @@ static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file, { struct kvm_s2_mmu *mmu = m->i_private; struct kvm *kvm = kvm_s2_mmu_to_kvm(mmu); - struct kvm_pgtable *pgtable; int ret; if (!kvm_get_kvm_safe(kvm)) return -ENOENT; - pgtable = mmu->pgt; - - ret = single_open(file, show, pgtable); + ret = single_open(file, show, mmu); if (ret < 0) kvm_put_kvm(kvm); return ret; -- 2.43.0