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Desmond Cheong Zhi Xi f671a691e2 fcntl: fix potential deadlocks for &fown_struct.lock
Syzbot reports a potential deadlock in do_fcntl:

========================================================
WARNING: possible irq lock inversion dependency detected
5.12.0-syzkaller #0 Not tainted
--------------------------------------------------------
syz-executor132/8391 just changed the state of lock:
ffff888015967bf8 (&f->f_owner.lock){.+..}-{2:2}, at: f_getown_ex fs/fcntl.c:211 [inline]
ffff888015967bf8 (&f->f_owner.lock){.+..}-{2:2}, at: do_fcntl+0x8b4/0x1200 fs/fcntl.c:395
but this lock was taken by another, HARDIRQ-safe lock in the past:
 (&dev->event_lock){-...}-{2:2}

and interrupts could create inverse lock ordering between them.

other info that might help us debug this:
Chain exists of:
  &dev->event_lock --> &new->fa_lock --> &f->f_owner.lock

 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&f->f_owner.lock);
                               local_irq_disable();
                               lock(&dev->event_lock);
                               lock(&new->fa_lock);
  <Interrupt>
    lock(&dev->event_lock);

 *** DEADLOCK ***

This happens because there is a lock hierarchy of
&dev->event_lock --> &new->fa_lock --> &f->f_owner.lock
from the following call chain:

  input_inject_event():
    spin_lock_irqsave(&dev->event_lock,...);
    input_handle_event():
      input_pass_values():
        input_to_handler():
          evdev_events():
            evdev_pass_values():
              spin_lock(&client->buffer_lock);
              __pass_event():
                kill_fasync():
                  kill_fasync_rcu():
                    read_lock(&fa->fa_lock);
                    send_sigio():
                      read_lock_irqsave(&fown->lock,...);

However, since &dev->event_lock is HARDIRQ-safe, interrupts have to be
disabled while grabbing &f->f_owner.lock, otherwise we invert the lock
hierarchy.

Hence, we replace calls to read_lock/read_unlock on &f->f_owner.lock,
with read_lock_irq/read_unlock_irq.

Reported-and-tested-by: syzbot+e6d5398a02c516ce5e70@syzkaller.appspotmail.com
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
2021-08-21 16:20:27 -04:00
arch RISC-V Fixes for 5.14-rc7 2021-08-21 11:04:26 -07:00
block block-5.14-2021-08-20 2021-08-21 08:11:22 -07:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto crypto: drbg - select SHA512 2021-07-16 15:49:31 +08:00
Documentation RISC-V Fixes for 5.14-rc7 2021-08-21 11:04:26 -07:00
drivers Two clk driver fixes 2021-08-21 11:27:16 -07:00
fs fcntl: fix potential deadlocks for &fown_struct.lock 2021-08-21 16:20:27 -04:00
include Merge branch 'akpm' (patches from Andrew) 2021-08-20 13:08:56 -07:00
init init: Suppress wrong warning for bootconfig cmdline parameter 2021-08-12 13:35:57 -04:00
ipc Merge branch 'akpm' (patches from Andrew) 2021-07-02 12:08:10 -07:00
kernel Networking fixes for 5.14-rc7, including fixes from bpf, wireless and 2021-08-19 12:33:43 -07:00
lib lib: use PFN_PHYS() in devmem_is_allowed() 2021-08-13 14:09:32 -10:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm hugetlb: don't pass page cache pages to restore_reserve_on_error 2021-08-20 11:31:42 -07:00
net mptcp: full fully established support after ADD_ADDR 2021-08-19 12:16:54 +01:00
samples Networking fixes for 5.14-rc2, including fixes from bpf and netfilter. 2021-07-14 09:24:32 -07:00
scripts Kbuild fixes for v5.14 (2nd) 2021-08-07 10:03:02 -07:00
security bpf: Add lockdown check for probe_write_user helper 2021-08-10 10:10:10 +02:00
sound another sound-fixes for 5.14-rc7 2021-08-20 12:31:10 -07:00
tools Networking fixes for 5.14-rc7, including fixes from bpf, wireless and 2021-08-19 12:33:43 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Do not leak memory for duplicate debugfs directories 2021-08-04 06:02:03 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap m68k updates for v5.14 2021-06-28 14:01:03 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -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 Merge branch 'akpm' (patches from Andrew) 2021-08-20 13:08:56 -07:00
Makefile Linux 5.14-rc6 2021-08-15 13:40:53 -10:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.