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=1794046042; b=PLZAjgomfgkk6WHy4VvdAWSwbKjbLc8GYndi7juKTeXRz7ZAZiplnwT1FHK3F4QOoss3 8u2r7p6yl4KPXCyjoMpP6g8CsuiTanJV2+bimDOFn9jgypqfKDNr7/JFHf+3wXlYhPRdJ hsdhue8Fy/JPoMbtLTjVfjkV7QnDqDdE1CWpp/oXW+FJ9TIN7z8Vrq9s17zPVzB/nxRso 8Kk+t5zvraJaSOtX3WHhNHXRN4uHpodYTogvhb1PYp/EqHhyT0nkLzPxsbt0bXa2xFDzN RnuAcULlLCqnnHUwxu4+zSqwWE3GF4p0lexNT/5zVTekDZq0teZMuAxY9N2S1o1C0wA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794046042; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=8TJOsNe0VknxuEyhFpmlsaOaqv8ZhxmO7iLpcOPm5z0=; b=K54Xt8/g1c59SK1RqkSnqPifahpgbJHtwV6QugWdKxgiIg9pi3/eOW2zToz7EEgccRvA YGjDj9UiYDxSsRWLtlyNosIWzUI9Vod1Gt37I1fCqcv+bwS/5vKxmCf9U8/qBI0UsLxIq 1+9s1TWof01agVDVshdOTYtMX75GWU2D/E6Y7MQPgmTavuBeWR0/3RacV2w/B9eIyC5Ge VLFZKt/oQEjjX+03oHyv5uU3SItHjYtqXZRBaeKBWbFP2F8wDio+0JQsgJZrkqrf1CNWT d3+Ly3WwUOXTn1NK+xcCVtf3mgopa/cu41GMUDXeVg9A8+G55s+HzkN1tLKJhBUhKCA== 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=MrEyIOS5; 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 7EBE8606A32C for ; Sat, 7 Nov 2026 10:07:21 +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=MrEyIOS5 Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1B071F008A1; Sat, 7 Nov 2026 10:07:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794046041; bh=8TJOsNe0VknxuEyhFpmlsaOaqv8ZhxmO7iLpcOPm5z0=; h=From:To:Cc:Subject:Date; b=MrEyIOS5khmJV/U51LY03fk1uyFT5uj7G3HrgVOLqh9P9oG2skp9IThSfHg8M6liL OgjACH0Pco60QvcLTFP1LvFtgZEvf0fbf0ExelKrhhShXOKJ6I5VI7B4eCdN2VhXAl mVTuMOVDN9oAzJA0tut8QSnH2vU9AWmmIXX5tpN1gg9kgQ+bAIAXOPRnCWaFoxQGVW fIWFvZQAWd/+tLVWRB7W+rIHPQIEoRvjV6IDWIceYIpNAWgHGuSXy925CFvIOLfw7A jw7WS+M65zEi2tuENOQTW0/a/puUgI6hdmZzxKZIcY6qgUYFlAJdfJUhuqTIwoLnFv hL5cS1Gf/5dxA== From: Sasha Levin To: weilin.chang@arm.com, sashiko-bot@kernel.org, vdonnefort@google.com, itaru.kitayama@fujitsu.com, maz@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] KVM: arm64: ptdump: Check the page tables aren't freed when accessing" failed to apply to 6.18-stable tree Date: Sat, 7 Nov 2026 05:07:19 -0500 Message-ID: <20261107050719-failed-6.18-7d7199bdf77a@kernel.org> X-Mailer: git-send-email 2.53.0 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 The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 7d7199bdf77a3a6ed74d0037133f435a7febe97c # git commit -s git send-email --to '' --in-reply-to '20261107050719-failed-6.18-7d7199bdf77a@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 7d7199bdf77a3a6ed74d0037133f435a7febe97c Mon Sep 17 00:00:00 2001 From: Wei-Lin Chang Date: Thu, 24 Sep 2026 10:49:50 +0100 Subject: [PATCH] KVM: arm64: ptdump: Check the page tables aren't freed when accessing 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/ 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 --- 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 69899797dbad8..b5a0584260e8b 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(read_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(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; } @@ -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; -- 2.53.0