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 8814618A6A7; Sun, 22 Jun 2025 22:37:24 +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=1750631844; cv=none; b=hBFks4+HNEM6cNJ4pu88LAJduyMKZWYkpUqtFvXHajDJLyP9NsQlPkioZPR6I5BmgwrFby/ZcLMXMIK96ivgaDQUGzX9IF7fbYf/j/yBY6Qj0kAu6pc9LM8VLdTzILjPtyHMVUO+NoMZB5Ri6x5qTiNYMOolBP25tHO9RrFW/wA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750631844; c=relaxed/simple; bh=SUQWD67K+42SU8c8u3gHkfIQcQFJm+LViFJSIVNhtH8=; h=Date:To:From:Subject:Message-Id; b=iSK2IdGB+ucpkL5QOw+7LaBNfrOrhRkA011Vob5hqaGqTec2kTFmaFG2kak1S4z8ObqYqNmqispk3BvyRB6VUhNRbRBex+6dW462WwoknBLc37OCLv2HfuWsLZEBQ23cIWR1wr555QZhdd3xq0twfKga/JcRqKXTgJnet0XBw8A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=wi349IA0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="wi349IA0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 034EAC4CEE3; Sun, 22 Jun 2025 22:37:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1750631844; bh=SUQWD67K+42SU8c8u3gHkfIQcQFJm+LViFJSIVNhtH8=; h=Date:To:From:Subject:From; b=wi349IA0kS85+9SlxZG4STKi9N6bXAUStvJKSTrboNQ1f5c8bQqiqXKdQgjuktc1r DNaU0r8NEcjDimubWayE5EFycwgnzDZkGcbjlR3XZPQR5VnekwJs+aL0eWNjwdzHli /MeivUYZhr4y/Ygy4BsGKhXfJQbJ82OHROGcf2Us= Date: Sun, 22 Jun 2025 15:37:23 -0700 To: mm-commits@vger.kernel.org,will@kernel.org,svens@linux.ibm.com,stable@vger.kernel.org,ryan.roberts@arm.com,paul.walmsley@sifive.com,palmer@dabbelt.com,hca@linux.ibm.com,gor@linux.ibm.com,gerald.schaefer@linux.ibm.com,catalin.marinas@arm.com,borntraeger@linux.ibm.com,agordeev@linux.ibm.com,anshuman.khandual@arm.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd.patch added to mm-new branch Message-Id: <20250622223724.034EAC4CEE3@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() has been added to the -mm mm-new branch. Its filename is mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Note, mm-new is a provisional staging ground for work-in-progress patches, and acceptance into mm-new is a notification for others take notice and to finish up reviews. Please do not hesitate to respond to review feedback and post updated versions to replace or incrementally fixup patches in mm-new. Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Anshuman Khandual Subject: mm/ptdump: take the memory hotplug lock inside ptdump_walk_pgd() Date: Fri, 20 Jun 2025 10:54:27 +0530 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 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 --- 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~mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd +++ a/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~mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd +++ a/arch/riscv/mm/ptdump.c @@ -6,7 +6,6 @@ #include #include #include -#include #include #include @@ -413,9 +412,7 @@ 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~mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd +++ a/arch/s390/mm/dump_pagetables.c @@ -247,11 +247,9 @@ 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~mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd +++ a/mm/ptdump.c @@ -176,6 +176,7 @@ 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_debug(mm, range->start, range->end, @@ -183,6 +184,7 @@ void ptdump_walk_pgd(struct ptdump_state range++; } mmap_write_unlock(mm); + put_online_mems(); /* Flush out the last page */ st->note_page_flush(st); _ Patches currently in -mm which might be from anshuman.khandual@arm.com are mm-ptdump-take-the-memory-hotplug-lock-inside-ptdump_walk_pgd.patch