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Hugh Dickins 48b94e4998 mm/khugepaged: fix collapse_pte_mapped_thp() to allow anon_vma 
commit ab0c3f1251 upstream.

uprobe_write_opcode() uses collapse_pte_mapped_thp() to restore huge pmd,
when removing a breakpoint from hugepage text: vma->anon_vma is always set
in that case, so undo the prohibition.  And MADV_COLLAPSE ought to be able
to collapse some page tables in a vma which happens to have anon_vma set
from CoWing elsewhere.

Is anon_vma lock required?  Almost not: if any page other than expected
subpage of the non-anon huge page is found in the page table, collapse is
aborted without making any change.  However, it is possible that an anon
page was CoWed from this extent in another mm or vma, in which case a
concurrent lookup might look here: so keep it away while clearing pmd (but
perhaps we shall go back to using pmd_lock() there in future).

Note that collapse_pte_mapped_thp() is exceptional in freeing a page table
without having cleared its ptes: I'm uneasy about that, and had thought
pte_clear()ing appropriate; but exclusive i_mmap lock does fix the
problem, and we would have to move the mmu_notification if clearing those
ptes.

What this fixes is not a dangerous instability.  But I suggest Cc stable
because uprobes "healing" has regressed in that way, so this should follow
8d3c106e19 into those stable releases where it was backported (and may
want adjustment there - I'll supply backports as needed).

Link: https://lkml.kernel.org/r/b740c9fb-edba-92ba-59fb-7a5592e5dfc@google.com
Fixes: 8d3c106e19 ("mm/khugepaged: take the right locks for page table retraction")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: <stable@vger.kernel.org>    [5.4+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-01-24 07:24:33 +01:00
arch LoongArch: Add HWCAP_LOONGARCH_CPUCFG to elf_hwcap 2023-01-24 07:24:33 +01:00
block block: handle bio_split_to_limits() NULL return 2023-01-18 11:58:33 +01:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto crypto: tcrypt - Fix multibuffer skcipher speed test mem leak 2022-12-31 13:32:34 +01:00
Documentation drm/vmwgfx: Remove vmwgfx_hashtab 2023-01-18 11:58:28 +01:00
drivers Add exception protection processing for vd in axi_chan_handle_err function 2023-01-24 07:24:33 +01:00
fs nilfs2: fix general protection fault in nilfs_btree_insert() 2023-01-24 07:24:33 +01:00
include btrfs: fix trace event name typo for FLUSH_DELAYED_REFS 2023-01-24 07:24:30 +01:00
init gcc: disable -Warray-bounds for gcc-11 too 2023-01-14 10:33:43 +01:00
io_uring io_uring/io-wq: only free worker if it was allocated for creation 2023-01-18 11:58:33 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: keep a reference to the mm, in case the task is dead. 2023-01-24 07:24:31 +01:00
lib kunit: alloc_string_stream_fragment error handling bug fix 2023-01-12 12:02:41 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/khugepaged: fix collapse_pte_mapped_thp() to allow anon_vma 2023-01-24 07:24:33 +01:00
net wifi: mac80211: fix initialization of rx->link and rx->link_sta 2023-01-24 07:24:33 +01:00
rust Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
samples samples: vfio-mdev: Fix missing pci_disable_device() in mdpy_fb_probe() 2022-12-31 13:32:42 +01:00
scripts - Handle different output of readelf on different distros running 2022-11-27 12:08:17 -08:00
security device_cgroup: Roll back to original exceptions after copy failure 2023-01-07 11:11:56 +01:00
sound ALSA: usb-audio: Fix possible NULL pointer dereference in snd_usb_pcm_has_fixed_rate() 2023-01-18 11:58:32 +01:00
tools proc: fix PIE proc-empty-vm, proc-pid-vm tests 2023-01-24 07:24:33 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt Merge branch 'kvm-dwmw2-fixes' into HEAD 2022-11-23 18:59:45 -05:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
Makefile Linux 6.1.7 2023-01-18 11:58:34 +01:00
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.