From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 890941DC997; Mon, 18 Aug 2025 13:41:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755524503; cv=none; b=GPhaWJ06rdqaaLjR0NxlwlxmVHv+SI31X4E1YzTVmeIkGNR1zIeo3qQy+uYtUOyX/qYQ8EnepK28chiR0/YKNyGd73voV4An1AVWcCQmv0b8TnEx4tkda69QkBeY6zSkbWq2j2NzPEE9+W+thJY3rLGQF7LfNxXM6GbYiJBjutg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755524503; c=relaxed/simple; bh=s0+3h5vupvTfojArTr1oKC9Ck7mRWikjAWMC3mY3A1s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LcSyijekJr4tlJt2zT6UIhMYvCGazNF4N6wS3RVTzdN4W8IBDn+dFPnDpNDzEDNOXdR8FWvuZJyGcXjjXWhgo0+onCOwGhv1aLvkVHKyUOWJHg/a2+st2Cob27AZH9S+HLP0/nCeUQoYP+1wjV9TNwBhZIzaIL1wXg14FeeEUOA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=mcIlBtkn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="mcIlBtkn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D081DC116C6; Mon, 18 Aug 2025 13:41:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755524503; bh=s0+3h5vupvTfojArTr1oKC9Ck7mRWikjAWMC3mY3A1s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mcIlBtknM8DOVZOFnCzi0ZcX8gbHjnjQCzX0+x2t+F6pldjMzvHuDe+7GDKV1tonH oS/zgJXlRJLDolpww6HqHGKFp01UDp/1TB90J0J5yyY1TFjgS44MmqZgSIzZR4Kb6M NuYSNPH5/EvGKrc14T7aQTcnoNZOgMYPlWMr7WOs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Anshuman Khandual , David Hildenbrand , Dev Jain , Catalin Marinas , Will Deacon , Ryan Roberts , Paul Walmsley , Palmer Dabbelt , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Andrew Morton Subject: [PATCH 6.15 492/515] mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() Date: Mon, 18 Aug 2025 14:47:58 +0200 Message-ID: <20250818124517.379068002@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250818124458.334548733@linuxfoundation.org> References: <20250818124458.334548733@linuxfoundation.org> User-Agent: quilt/0.68 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 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Anshuman Khandual commit 59305202c67fea50378dcad0cc199dbc13a0e99a upstream. Memory hot remove unmaps and tears down various kernel page table regions as required. The ptdump code can race with concurrent modifications of the kernel page tables. When leaf entries are modified concurrently, the dump code may log stale or inconsistent information for a VA range, but this is otherwise not harmful. But when intermediate levels of kernel page table are freed, the dump code will continue to use memory that has been freed and potentially reallocated for another purpose. In such cases, the ptdump code may dereference bogus addresses, leading to a number of potential problems. To avoid the above mentioned race condition, platforms such as arm64, riscv and s390 take memory hotplug lock, while dumping kernel page table via the sysfs interface /sys/kernel/debug/kernel_page_tables. Similar race condition exists while checking for pages that might have been marked W+X via /sys/kernel/debug/kernel_page_tables/check_wx_pages which in turn calls ptdump_check_wx(). Instead of solving this race condition again, let's just move the memory hotplug lock inside generic ptdump_check_wx() which will benefit both the scenarios. Drop get_online_mems() and put_online_mems() combination from all existing platform ptdump code paths. Link: https://lkml.kernel.org/r/20250620052427.2092093-1-anshuman.khandual@arm.com Fixes: bbd6ec605c0f ("arm64/mm: Enable memory hot remove") Signed-off-by: Anshuman Khandual Acked-by: David Hildenbrand Reviewed-by: Dev Jain Acked-by: Alexander Gordeev [s390] Cc: Catalin Marinas Cc: Will Deacon Cc: Ryan Roberts Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Alexander Gordeev Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Sven Schnelle Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- arch/arm64/mm/ptdump_debugfs.c | 3 --- arch/riscv/mm/ptdump.c | 3 --- arch/s390/mm/dump_pagetables.c | 2 -- mm/ptdump.c | 2 ++ 4 files changed, 2 insertions(+), 8 deletions(-) --- a/arch/arm64/mm/ptdump_debugfs.c +++ b/arch/arm64/mm/ptdump_debugfs.c @@ -1,6 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 #include -#include #include #include @@ -9,9 +8,7 @@ static int ptdump_show(struct seq_file * { struct ptdump_info *info = m->private; - get_online_mems(); ptdump_walk(m, info); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); --- a/arch/riscv/mm/ptdump.c +++ b/arch/riscv/mm/ptdump.c @@ -6,7 +6,6 @@ #include #include #include -#include #include #include @@ -371,9 +370,7 @@ bool ptdump_check_wx(void) static int ptdump_show(struct seq_file *m, void *v) { - get_online_mems(); ptdump_walk(m, m->private); - put_online_mems(); return 0; } --- a/arch/s390/mm/dump_pagetables.c +++ b/arch/s390/mm/dump_pagetables.c @@ -205,11 +205,9 @@ static int ptdump_show(struct seq_file * .marker = markers, }; - get_online_mems(); mutex_lock(&cpa_mutex); ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); mutex_unlock(&cpa_mutex); - put_online_mems(); return 0; } DEFINE_SHOW_ATTRIBUTE(ptdump); --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -153,6 +153,7 @@ void ptdump_walk_pgd(struct ptdump_state { const struct ptdump_range *range = st->range; + get_online_mems(); mmap_write_lock(mm); while (range->start != range->end) { walk_page_range_novma(mm, range->start, range->end, @@ -160,6 +161,7 @@ void ptdump_walk_pgd(struct ptdump_state range++; } mmap_write_unlock(mm); + put_online_mems(); /* Flush out the last page */ st->note_page(st, 0, -1, 0);