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=1794311528; b=xFUtzE2V1OJaNFcP5GKTaqKOzzpLBssdMxEhZ7MmXcSKPOoK+K1xq1yGPykJr6v21a2z jic9DbLocE2Pdsojg0KKqRmI8p26+/5F6J3nXol6cx8uwnnJog/I4FBCa8+Hk1erZ4BR6 l1cDQ/TYUPsW7tBjIh0ixpsp1RXKqRKqfDZL3+uApCGXANaN26X5iqpCvDQAu/haSLwVU znWiO9hCtdfS3m1NwKiIc+5fhz6Nd8v0F3M0sDERSMIRCb74rXsQRiGaijCNv80gb+I7B D0PSrT5pfoaNIi0O0M2Fvs1jjEl3JJSgtSg0ck8zu7U6y1FqUTzeHlriQl2ElaIymwg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794311528; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=EmWfwJx/dCnMD2bFvmhriLTUAJGpje8dIiK4NGgpbcc=; b=ZgtcrK3qvg/80i7j9Z2ZvvdkgT+uNmssnwLos5gMoI4Dsp/wZf2AjnbmkNYMuf09+b2A t+36bWB2JRXCY03+i/5p8h6AzsR6zJrfoCFRNBBq7gY4Ieg/Pe7zjRUoRzJk6KgU/QqGD h2HsLPXSqYRiNnrhaqmxcNLJoH+WalliM3Z9K1yOSf+HNbl/0sHgI+8fbABgKQ62DD/8B vWUake6bt8JWSkh1DOZXOF2dpPPfmodopITkWQUol/YrHo0NckdD/WK2FDNr23ue9uIOg MbvrLmm2YQqA8Nn90MoP4yRlPv1mwfbs8fji1B76Y/vZgYMV1453HnPwMm265Urpaew== 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=d0VIMz3l; 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 00266606B595 for ; Tue, 10 Nov 2026 11:52:07 +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=d0VIMz3l Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF89D1F008A1; Tue, 10 Nov 2026 11:52:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794311527; bh=EmWfwJx/dCnMD2bFvmhriLTUAJGpje8dIiK4NGgpbcc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=d0VIMz3lzzQ/32fw4+V2RES8N6Z8WllRpiZ9lcY4xsvDpJEBFNvgJQx0V1Hx4wmpW E69FGhlF8PwhqN6vCGc5I1Gn7KFBX4CvXz40r7hsySCSpMxlp1gkgvCL86DAKRqZDF 8Mkde8en3dHj0n+X4+j4QBNyunYpV/OOHyJNeKIDp3bnug3N/4/zTY5/CXNMv42a81 vYq0GfD0kx9mR/BQY8zm1QMVUa5UXdml0TdvlV/GOe62F5SdD4l71VAFSmAO46vTJo 1d+w5idMwjSb6Ro732X4f5bpfpzvJybPfOH/EJcjApw/CrS7TWKgzEPHx1Wb/LspF0 XCsCU9WiY6/JQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Wei-Lin Chang , Sashiko AI , Vincent Donnefort , Itaru Kitayama , Marc Zyngier , Sasha Levin Subject: [PATCH 6.12.y] KVM: arm64: ptdump: Check the page tables aren't freed when accessing Date: Tue, 10 Nov 2026 06:52:05 -0500 Message-ID: <20261110115143.876583-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261107051745-failed-6.12-7d7199bdf77a@kernel.org> References: <20261107051745-failed-6.12-7d7199bdf77a@kernel.org> 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 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