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=1794591371; b=zwjoeKaKJ3j/roxeiLtWpmYvZA8mUIVG0rcvCv9YFnyzshUAt0XGG3T0e9qzyyMcp0Wj V1pld+UADTgobxeo5cgmKsCkbjmlN/K8d5Rg5uWp7hFP0e/TM65g6zP3JblOEFBIMRe02 9puEg4igF/rKIDc6M1X9Js9I9H2/YyuAEfuSsEW33pOo/bbz+WDr3x5sgaN9nVbAAkv2S tbFslsSHH7bF5JNZhbaKhln9SaVt/xIko2mMRG8WvwNxi4gA03MvfS+GPyaQXq22vBkhe 7urXAelpO1//NfjMQLo1zap5ATdcqVyTkVAH7M05UPMVBtSOExZqzmpLOJ83/pQDUMA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794591371; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=mCWr/MY973CxA9Q6Zb1Q8CcjeDypZoQTWWxz1jkh3PI=; b=u+AccwIZBBaGyUefdiPWqenzR1MVhLkZpvhNyV02WA862DsYdEB8HoeGH7PRupEjIzEN /zvJrsGskeIhsRBHEAlUlfS4zF1emQ38vzTAaxgWY3cgfXDVBBrjJLgKY5Ju7OnRVubfe bWWx21mFmXMc0kshw1zuBpcLPA3ATeaGALHMeImpBi7Cn3iwnTS87jEVQp4hcjzdEf++P JdCwYKspFb4RnfboyKGtagXH0GAAew6IEM+Z5cwzrh2OHPaZoffzuZzZJg8dNj2lhd3kt B2Pv9H3jCvZIdEvV77/rjAQVsUjSPU98LOinWp6F7JYgcuRyCheA2AQ6THAMQWdRbvw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=hnx4MA03; 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 51A09606EDAF; Fri, 13 Nov 2026 17:36:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=hnx4MA03 Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3AC51F000C4; Fri, 13 Nov 2026 17:36:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794591371; bh=mCWr/MY973CxA9Q6Zb1Q8CcjeDypZoQTWWxz1jkh3PI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=hnx4MA03rneYQnk7Vf/G0CWh1jByTi0d7Wpxfl5A7gwDnt0pfCLTznCOHKVsYwvnM EoPse5l5UIW/9hEfy0Lo/bsmhM+9sv2IGfY4ylZzgMwX7p+MUR6O0PWDaELVPlQXzz umI6ve9eTknTr9SmpaXxWo8bmGp+wSjJuZzfZmS0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sashiko AI , Vincent Donnefort , Itaru Kitayama , Wei-Lin Chang , Marc Zyngier , Sasha Levin Subject: [PATCH 6.12 431/670] KVM: arm64: ptdump: Check the page tables arent freed when accessing Date: Fri, 13 Nov 2026 10:49:55 -0500 Message-ID: <20261113153826.350338102@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev 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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wei-Lin Chang [ Upstream commit 7d7199bdf77a3a6ed74d0037133f435a7febe97c ] 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/ Reviewed-by: Vincent Donnefort Tested-by: Vincent Donnefort Tested-by: Itaru Kitayama Signed-off-by: Wei-Lin Chang Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260924094951.727352-2-weilin.chang@arm.com Signed-off-by: Marc Zyngier [ sashal: Cached ia_bits alongside start_level under mmu_lock to support the existing IPA range initialization during parser creation. ] Signed-off-by: Sasha Levin --- arch/arm64/kvm/ptdump.c | 50 +++++++++++++++++++++++++++++------------ 1 file changed, 36 insertions(+), 14 deletions(-) diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c index e4a342e903e25..ce9a64715bcd2 100644 --- a/arch/arm64/kvm/ptdump.c +++ b/arch/arm64/kvm/ptdump.c @@ -97,22 +97,35 @@ static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm *kvm) { struct kvm_ptdump_guest_state *st; struct kvm_s2_mmu *mmu = &kvm->arch.mmu; - struct kvm_pgtable *pgtable = mmu->pgt; + s8 start_level; + u32 ia_bits; int ret; + /* + * We only need the pgt start level and IPA size to initialize the ptdump, + * get them 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(read_lock, &kvm->mmu_lock) { + if (!mmu->pgt) + return ERR_PTR(-ENOENT); + start_level = mmu->pgt->start_level; + ia_bits = mmu->pgt->ia_bits; + } + st = kzalloc(sizeof(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); } st->ipa_marker[0].name = "Guest IPA"; - st->ipa_marker[1].start_address = BIT(pgtable->ia_bits); - st->range[0].end = BIT(pgtable->ia_bits); + st->ipa_marker[1].start_address = BIT(ia_bits); + st->range[0].end = BIT(ia_bits); st->kvm = kvm; st->parser_state = (struct ptdump_pg_state) { @@ -141,9 +154,11 @@ static int kvm_ptdump_guest_show(struct seq_file *m, void *unused) parser_state->seq = m; - write_lock(&kvm->mmu_lock); + guard(write_lock)(&kvm->mmu_lock); + if (!mmu->pgt) + return 0; + ret = kvm_pgtable_walk(mmu->pgt, 0, BIT(mmu->pgt->ia_bits), &walker); - write_unlock(&kvm->mmu_lock); return ret; } @@ -193,17 +208,27 @@ 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(read_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(read_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; } @@ -211,15 +236,12 @@ static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file, int (*show)(struct seq_file *, void *)) { struct kvm *kvm = m->i_private; - struct kvm_pgtable *pgtable; int ret; if (!kvm_get_kvm_safe(kvm)) return -ENOENT; - pgtable = kvm->arch.mmu.pgt; - - ret = single_open(file, show, pgtable); + ret = single_open(file, show, &kvm->arch.mmu); if (ret < 0) kvm_put_kvm(kvm); return ret; -- 2.53.0