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Filename Latest commit message Latest commit date
Nico Pache 0441d3e95b oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup 
commit e4a38402c36e42df28eb1a5394be87e6571fb48a upstream.

The pthread struct is allocated on PRIVATE|ANONYMOUS memory [1] which
can be targeted by the oom reaper.  This mapping is used to store the
futex robust list head; the kernel does not keep a copy of the robust
list and instead references a userspace address to maintain the
robustness during a process death.

A race can occur between exit_mm and the oom reaper that allows the oom
reaper to free the memory of the futex robust list before the exit path
has handled the futex death:

    CPU1                               CPU2
    --------------------------------------------------------------------
    page_fault
    do_exit "signal"
    wake_oom_reaper
                                        oom_reaper
                                        oom_reap_task_mm (invalidates mm)
    exit_mm
    exit_mm_release
    futex_exit_release
    futex_cleanup
    exit_robust_list
    get_user (EFAULT- can't access memory)

If the get_user EFAULT's, the kernel will be unable to recover the
waiters on the robust_list, leaving userspace mutexes hung indefinitely.

Delay the OOM reaper, allowing more time for the exit path to perform
the futex cleanup.

Reproducer: https://gitlab.com/jsavitz/oom_futex_reproducer

Based on a patch by Michal Hocko.

Link: https://elixir.bootlin.com/glibc/glibc-2.35/source/nptl/allocatestack.c#L370 [1]
Link: https://lkml.kernel.org/r/20220414144042.677008-1-npache@redhat.com
Fixes: 2129258024 ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
Signed-off-by: Joel Savitz <jsavitz@redhat.com>
Signed-off-by: Nico Pache <npache@redhat.com>
Co-developed-by: Joel Savitz <jsavitz@redhat.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Herton R. Krzesinski <herton@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joel Savitz <jsavitz@redhat.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-04-27 13:50:48 +02:00
arch stat: fix inconsistency between struct stat and struct compat_stat 2022-04-27 13:50:48 +02:00
block Revert "Revert "block, bfq: honor already-setup queue merges"" 2022-04-15 14:18:23 +02:00
certs
crypto crypto: authenc - Fix sleep in atomic context in decrypt_tail 2022-04-15 14:18:04 +02:00
Documentation dt-bindings: spi: mxic: The interrupt property is not mandatory 2022-04-15 14:18:30 +02:00
drivers EDAC/synopsys: Read the error count from the correct register 2022-04-27 13:50:48 +02:00
fs stat: fix inconsistency between struct stat and struct compat_stat 2022-04-27 13:50:48 +02:00
include oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup 2022-04-27 13:50:48 +02:00
init init/main.c: return 1 from handled __setup() functions 2022-04-15 14:18:35 +02:00
ipc
kernel tracing: Dump stacktrace trigger to the corresponding instance 2022-04-27 13:50:45 +02:00
lib lz4: fix LZ4_decompress_safe_partial read out of bound 2022-04-15 14:18:39 +02:00
LICENSES
mm oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup 2022-04-27 13:50:48 +02:00
net netlink: reset network and mac headers in netlink_dump() 2022-04-27 13:50:47 +02:00
samples
scripts gcc-plugins: latent_entropy: use /dev/urandom 2022-04-20 09:19:38 +02:00
security Fix incorrect type in assignment of ipv6 port for audit 2022-04-15 14:18:22 +02:00
sound ALSA: usb-audio: Fix undefined behavior due to shift overflowing the constant 2022-04-27 13:50:47 +02:00
tools selftests: mlxsw: vxlan_flooding: Prevent flooding of unwanted packets 2022-04-27 13:50:47 +02:00
usr
virt KVM: Prevent module exit until all VMs are freed 2022-04-15 14:18:27 +02:00
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.cocciconfig
.get_maintainer.ignore
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.gitignore
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COPYING
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Kconfig
MAINTAINERS
Makefile Linux 5.4.190 2022-04-20 09:19:40 +02:00
README

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.