From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
Alexey Dobriyan <adobriyan@gmail.com>,
Mike Rapoport <rppt@kernel.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Oscar Salvador <osalvador@suse.de>,
Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>,
Alex Shi <alex.shi@linux.alibaba.com>,
Steven Price <steven.price@arm.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Aili Yao <yaoaili@kingsoft.com>, Jiri Bohac <jbohac@suse.cz>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Wei Liu <wei.liu@kernel.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
linux-hyperv@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v3 0/6] fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages
Date: Wed, 26 May 2021 11:30:35 +0200 [thread overview]
Message-ID: <20210526093041.8800-1-david@redhat.com> (raw)
Looking for places where the kernel might unconditionally read
PageOffline() pages, I stumbled over /proc/kcore; turns out /proc/kcore
needs some more love to not touch some other pages we really don't want to
read -- i.e., hwpoisoned ones.
Examples for PageOffline() pages are pages inflated in a balloon,
memory unplugged via virtio-mem, and partially-present sections in
memory added by the Hyper-V balloon.
When reading pages inflated in a balloon, we essentially produce
unnecessary load in the hypervisor; holes in partially present sections in
case of Hyper-V are not accessible and already were a problem for
/proc/vmcore, fixed in makedumpfile by detecting PageOffline() pages. In
the future, virtio-mem might disallow reading unplugged memory -- marked
as PageOffline() -- in some environments, resulting in undefined behavior
when accessed; therefore, I'm trying to identify and rework all these
(corner) cases.
With this series, there is really only access via /dev/mem, /proc/vmcore
and kdb left after I ripped out /dev/kmem. kdb is an advanced corner-case
use case -- we won't care for now if someone explicitly tries to do nasty
things by reading from/writing to physical addresses we better not touch.
/dev/mem is a use case we won't support for virtio-mem, at least for now,
so we'll simply disallow mapping any virtio-mem memory via /dev/mem next.
/proc/vmcore is really only a problem when dumping the old kernel via
something that's not makedumpfile (read: basically never), however, we'll
try sanitizing that as well in the second kernel in the future.
Tested via kcore_dump:
https://github.com/schlafwandler/kcore_dump
v2 -> v3:
- "mm: introduce page_offline_(begin|end|freeze|thaw) to synchronize
setting PageOffline()"
-- Rephrased a comment as suggested by Mike
- Collected acks and rbs
v1 -> v2:
- Dropped "mm: rename and move page_is_poisoned()"
- "fs/proc/kcore: don't read offline sections, logically offline pages ..."
-- Add is_page_hwpoison() in page-flags.h along with a comment
- "mm: introduce page_offline_(begin|end|freeze|thaw) to ..."
-- s/unfreeze/thaw/
-- Add a comment to PageOffline documentation in page-flags.h
- "virtio-mem: use page_offline_(start|end) when setting PageOffline()"
-- Extend patch description
- "fs/proc/kcore: use page_offline_(freeze|thaw)"
-- Simplify freeze/thaw logic
- Collected acks/rbs
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Aili Yao <yaoaili@kingsoft.com>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: linux-hyperv@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-mm@kvack.org
David Hildenbrand (6):
fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER
fs/proc/kcore: pfn_is_ram check only applies to KCORE_RAM
fs/proc/kcore: don't read offline sections, logically offline pages
and hwpoisoned pages
mm: introduce page_offline_(begin|end|freeze|thaw) to synchronize
setting PageOffline()
virtio-mem: use page_offline_(start|end) when setting PageOffline()
fs/proc/kcore: use page_offline_(freeze|thaw)
drivers/virtio/virtio_mem.c | 2 ++
fs/proc/kcore.c | 67 ++++++++++++++++++++++++++++++-------
include/linux/kcore.h | 3 --
include/linux/page-flags.h | 22 ++++++++++++
mm/util.c | 40 ++++++++++++++++++++++
5 files changed, 118 insertions(+), 16 deletions(-)
base-commit: 6efb943b8616ec53a5e444193dccf1af9ad627b5
--
2.31.1
next reply other threads:[~2021-05-26 9:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-26 9:30 David Hildenbrand [this message]
2021-05-26 9:30 ` [PATCH v3 1/6] fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER David Hildenbrand
2021-05-26 9:30 ` [PATCH v3 2/6] fs/proc/kcore: pfn_is_ram check only applies to KCORE_RAM David Hildenbrand
2021-05-26 9:30 ` [PATCH v3 3/6] fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages David Hildenbrand
2021-05-26 9:30 ` [PATCH v3 4/6] mm: introduce page_offline_(begin|end|freeze|thaw) to synchronize setting PageOffline() David Hildenbrand
2021-05-26 9:30 ` [PATCH v3 5/6] virtio-mem: use page_offline_(start|end) when " David Hildenbrand
2021-05-26 9:30 ` [PATCH v3 6/6] fs/proc/kcore: use page_offline_(freeze|thaw) David Hildenbrand
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