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Alistair Popple 0dc45ca1ce mm/memremap.c: take a pgmap reference on page allocation 
ZONE_DEVICE pages have a struct dev_pagemap which is allocated by a
driver.  When the struct page is first allocated by the kernel in
memremap_pages() a reference is taken on the associated pagemap to ensure
it is not freed prior to the pages being freed.

Prior to 27674ef6c7 ("mm: remove the extra ZONE_DEVICE struct page
refcount") pages were considered free and returned to the driver when the
reference count dropped to one.  However the pagemap reference was not
dropped until the page reference count hit zero.  This would occur as part
of the final put_page() in memunmap_pages() which would wait for all pages
to be freed prior to returning.

When the extra refcount was removed the pagemap reference was no longer
being dropped in put_page().  Instead memunmap_pages() was changed to
explicitly drop the pagemap references.  This means that memunmap_pages()
can complete even though pages are still mapped by the kernel which can
lead to kernel crashes, particularly if a driver frees the pagemap.

To fix this drivers should take a pagemap reference when allocating the
page.  This reference can then be returned when the page is freed.

Link: https://lkml.kernel.org/r/12d155ec727935ebfbb4d639a03ab374917ea51b.1664366292.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Fixes: 27674ef6c7 ("mm: remove the extra ZONE_DEVICE struct page refcount")
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>

Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 		2022-10-12 18:51:49 -07:00
Documentation mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol 2022-10-03 14:03:36 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
arch mm: free device private pages have zero refcount 2022-10-12 18:51:49 -07:00
block block: kmsan: skip bio block merging logic for KMSAN 2022-10-03 14:03:23 -07:00
certs Kbuild updates for v5.20 2022-08-10 10:40:41 -07:00
crypto crypto: kmsan: disable accelerated configs under KMSAN 2022-10-03 14:03:22 -07:00
drivers mm: free device private pages have zero refcount 2022-10-12 18:51:49 -07:00
fs ext4,f2fs: fix readahead of verity data 2022-10-12 18:51:48 -07:00
include mm: free device private pages have zero refcount 2022-10-12 18:51:49 -07:00
init mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol 2022-10-03 14:03:36 -07:00
io_uring io_uring/net: save address for sendzc async execution 2022-08-25 07:52:30 -06:00
ipc ipc/shm: use VMA iterator instead of linked list 2022-09-26 19:46:21 -07:00
kernel mm/madvise: add file and shmem support to MADV_COLLAPSE 2022-10-03 14:03:33 -07:00
lib mm: free device private pages have zero refcount 2022-10-12 18:51:49 -07:00
mm mm/memremap.c: take a pgmap reference on page allocation 2022-10-12 18:51:49 -07:00
net Including fixes from ipsec and netfilter (with one broken Fixes tag). 2022-08-25 14:03:58 -07:00
samples Tracing updates for 5.20 / 6.0 2022-08-05 09:41:12 -07:00
scripts kmsan: add KMSAN runtime core 2022-10-03 14:03:19 -07:00
security security: kmsan: fix interoperability with auto-initialization 2022-10-03 14:03:23 -07:00
sound sound fixes for 6.0-rc2 2022-08-19 09:46:11 -07:00
tools mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol 2022-10-03 14:03:36 -07:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: Drop unnecessary initialization of "ops" in kvm_ioctl_create_device() 2022-08-19 04:05:43 -04:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.cocciconfig
…
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap .mailmap: update Luca Ceresoli's e-mail address 2022-08-28 14:02:46 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS drm for 5.20/6.0 2022-08-03 19:52:08 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS x86: kmsan: handle CPU entry area 2022-10-03 14:03:26 -07:00
Makefile kmsan: add KMSAN runtime core 2022-10-03 14:03:19 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.