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Jan Kara 6717900f77 select: Fix indefinitely sleeping task in poll_schedule_timeout() 
commit 68514dacf2 upstream.

A task can end up indefinitely sleeping in do_select() ->
poll_schedule_timeout() when the following race happens:

  TASK1 (thread1)             TASK2                   TASK1 (thread2)
  do_select()
    setup poll_wqueues table
    with 'fd'
                              write data to 'fd'
                                pollwake()
                                  table->triggered = 1
                                                      closes 'fd' thread1 is
                                                        waiting for
    poll_schedule_timeout()
      - sees table->triggered
      table->triggered = 0
      return -EINTR
    loop back in do_select()

But at this point when TASK1 loops back, the fdget() in the setup of
poll_wqueues fails.  So now so we never find 'fd' is ready for reading
and sleep in poll_schedule_timeout() indefinitely.

Treat an fd that got closed as a fd on which some event happened.  This
makes sure cannot block indefinitely in do_select().

Another option would be to return -EBADF in this case but that has a
potential of subtly breaking applications that excercise this behavior
and it happens to work for them.  So returning fd as active seems like a
safer choice.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-01-29 10:19:18 +01:00
arch mips,s390,sh,sparc: gup: Work around the "COW can break either way" issue 2022-01-27 09:04:34 +01:00
block block, bfq: fix use after free in bfq_bfqq_expire 2021-12-29 12:20:43 +01:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-22 11:47:51 +02:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-26 11:36:11 +01:00
Documentation Documentation: refer to config RANDOMIZE_BASE for kernel address-space randomization 2022-01-27 09:04:32 +01:00
drivers drm/i915: Flush TLBs before releasing backing store 2022-01-29 10:19:18 +01:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs select: Fix indefinitely sleeping task in poll_schedule_timeout() 2022-01-29 10:19:18 +01:00
include net_sched: restore "mpu xxx" handling 2022-01-27 09:04:33 +01:00
init pid: take a reference when initializing cad_pid 2021-06-10 13:24:06 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-08 08:50:11 +01:00
kernel cputime, cpuacct: Include guest time in user time in cpuacct.stat 2022-01-27 09:04:30 +01:00
lib ARM: 8800/1: use choice for kernel unwinders 2021-12-22 09:19:03 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm shmem: fix a race between shmem_unused_huge_shrink and shmem_evict_inode 2022-01-27 09:04:16 +01:00
net net: bridge: clear bridge's private skb space on xmit 2022-01-29 10:19:18 +01:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-26 11:36:11 +01:00
scripts scripts/dtc: dtx_diff: remove broken example from help text 2022-01-27 09:04:33 +01:00
security selinux: initialize proto variable in selinux_ip_postroute_compat() 2022-01-05 12:34:58 +01:00
sound ASoC: dpcm: prevent snd_soc_dpcm use after free 2022-01-27 09:04:31 +01:00
tools selftests/net: udpgso_bench_tx: fix dst ip argument 2022-01-05 12:34:59 +01:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: remember position in kvm->vcpus array 2021-09-26 13:39:46 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-09-26 18:01:31 +02:00
Makefile Linux 4.19.226 2022-01-27 09:04:34 +01:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.