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Shuai Xue 415fed694f ACPI: APEI: do not add task_work to kernel thread to avoid memory leak 
If an error is detected as a result of user-space process accessing a
corrupt memory location, the CPU may take an abort. Then the platform
firmware reports kernel via NMI like notifications, e.g. NOTIFY_SEA,
NOTIFY_SOFTWARE_DELEGATED, etc.

For NMI like notifications, commit 7f17b4a121 ("ACPI: APEI: Kick the
memory_failure() queue for synchronous errors") keep track of whether
memory_failure() work was queued, and make task_work pending to flush out
the queue so that the work is processed before return to user-space.

The code use init_mm to check whether the error occurs in user space:

    if (current->mm != &init_mm)

The condition is always true, becase _nobody_ ever has "init_mm" as a real
VM any more.

In addition to abort, errors can also be signaled as asynchronous
exceptions, such as interrupt and SError. In such case, the interrupted
current process could be any kind of thread. When a kernel thread is
interrupted, the work ghes_kick_task_work deferred to task_work will never
be processed because entry_handler returns to call ret_to_kernel() instead
of ret_to_user(). Consequently, the estatus_node alloced from
ghes_estatus_pool in ghes_in_nmi_queue_one_entry() will not be freed.
After around 200 allocations in our platform, the ghes_estatus_pool will
run of memory and ghes_in_nmi_queue_one_entry() returns ENOMEM. As a
result, the event failed to be processed.

    sdei: event 805 on CPU 113 failed with error: -2

Finally, a lot of unhandled events may cause platform firmware to exceed
some threshold and reboot.

The condition should generally just do

    if (current->mm)

as described in active_mm.rst documentation.

Then if an asynchronous error is detected when a kernel thread is running,
(e.g. when detected by a background scrubber), do not add task_work to it
as the original patch intends to do.

Fixes: 7f17b4a121 ("ACPI: APEI: Kick the memory_failure() queue for synchronous errors")
Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2022-10-04 16:04:41 +02:00
arch ACPI updates for 6.1-rc1 2022-10-03 13:19:53 -07:00
block block-6.0-2022-09-22 2022-09-24 08:22:53 -07:00
certs certs: make system keyring depend on built-in x509 parser 2022-09-24 04:31:18 +09:00
crypto crypto: blake2b: effectively disable frame size warning 2022-08-10 17:59:11 -07:00
Documentation ACPI updates for 6.1-rc1 2022-10-03 13:19:53 -07:00
drivers ACPI: APEI: do not add task_work to kernel thread to avoid memory leak 2022-10-04 16:04:41 +02:00
fs pstore revert for v6.0-rc8 2022-09-30 08:54:14 -07:00
include ACPI updates for 6.1-rc1 2022-10-03 13:19:53 -07:00
init arm64 fixes for -rc3 2022-08-26 11:32:53 -07:00
io_uring io_uring-6.0-2022-09-29 2022-09-30 09:28:39 -07:00
ipc Updates to various subsystems which I help look after. lib, ocfs2, 2022-08-07 10:03:24 -07:00
kernel RCU pull request for v6.1 2022-10-03 10:11:11 -07:00
lib Makefile.debug: re-enable debug info for .S files 2022-09-24 11:19:19 +09:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm One MAINTAINERS update, two MM fixes, both cc:stable 2022-10-01 09:13:29 -07:00
net Networking fixes for 6.0-rc8, including fixes from wifi and can. 2022-09-29 08:32:53 -07:00
samples Tracing updates for 5.20 / 6.0 2022-08-05 09:41:12 -07:00
scripts There's not a huge amount of activity in the docs tree this time around, 2022-10-03 10:23:32 -07:00
security Landlock fix for v6.0-rc4 2022-09-02 15:24:08 -07:00
sound ALSA: hda: intel-dsp-config: add missing RaptorLake PCI IDs 2022-09-22 13:50:33 +02:00
tools ACPI updates for 6.1-rc1 2022-10-03 13:19:53 -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 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: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap Qualcomm ARM64 DTS fixes for 6.0 2022-09-23 16:44:37 +02:00
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 ACPI updates for 6.1-rc1 2022-10-03 13:19:53 -07:00
Makefile Linux 6.0 2022-10-02 14:09:07 -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.