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Boqun Feng c6090fe788 locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps() 
[ Upstream commit 25016bd7f4 ]

Qian Cai reported a bug when PROVE_RCU_LIST=y, and read on /proc/lockdep
triggered a warning:

  [ ] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)
  ...
  [ ] Call Trace:
  [ ]  lock_is_held_type+0x5d/0x150
  [ ]  ? rcu_lockdep_current_cpu_online+0x64/0x80
  [ ]  rcu_read_lock_any_held+0xac/0x100
  [ ]  ? rcu_read_lock_held+0xc0/0xc0
  [ ]  ? __slab_free+0x421/0x540
  [ ]  ? kasan_kmalloc+0x9/0x10
  [ ]  ? __kmalloc_node+0x1d7/0x320
  [ ]  ? kvmalloc_node+0x6f/0x80
  [ ]  __bfs+0x28a/0x3c0
  [ ]  ? class_equal+0x30/0x30
  [ ]  lockdep_count_forward_deps+0x11a/0x1a0

The warning got triggered because lockdep_count_forward_deps() call
__bfs() without current->lockdep_recursion being set, as a result
a lockdep internal function (__bfs()) is checked by lockdep, which is
unexpected, and the inconsistency between the irq-off state and the
state traced by lockdep caused the warning.

Apart from this warning, lockdep internal functions like __bfs() should
always be protected by current->lockdep_recursion to avoid potential
deadlocks and data inconsistency, therefore add the
current->lockdep_recursion on-and-off section to protect __bfs() in both
lockdep_count_forward_deps() and lockdep_count_backward_deps()

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200312151258.128036-1-boqun.feng@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-04-17 10:48:42 +02:00
arch x86/boot: Use unsigned comparison for addresses 2020-04-17 10:48:41 +02:00
block block: Fix use-after-free issue accessing struct io_cq 2020-04-17 10:48:41 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: api - Fix race condition in crypto_spawn_alg 2020-02-11 04:34:05 -08:00
Documentation dt-bindings: net: FMan erratum A050385 2020-04-02 15:28:14 +02:00
drivers firmware: fix a double abort case with fw_load_sysfs_fallback 2020-04-17 10:48:42 +02:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs gfs2: Don't demote a glock until its revokes are written 2020-04-17 10:48:41 +02:00
include block: Fix use-after-free issue accessing struct io_cq 2020-04-17 10:48:41 +02:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 09:21:04 +01:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-28 16:38:49 +01:00
kernel locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps() 2020-04-17 10:48:42 +02:00
lib lib/stackdepot.c: fix global out-of-bounds in stack_slabs 2020-02-28 16:38:55 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm: mempolicy: require at least one nodeid for MPOL_PREFERRED 2020-04-13 10:45:06 +02:00
net Bluetooth: RFCOMM: fix ODEBUG bug in rfcomm_dev_ioctl 2020-04-13 10:45:14 +02:00
samples samples/bpf: Don't try to remove user's homedir on clean 2020-02-11 04:34:05 -08:00
scripts scripts/dtc: Remove redundant YYLOC global declaration 2020-04-02 15:28:17 +02:00
security selinux: ensure we cleanup the internal AVC counters on error in avc_update() 2020-02-24 08:34:43 +01:00
sound ASoC: jz4740-i2s: Fix divider written at incorrect offset in register 2020-04-13 10:45:11 +02:00
tools selftests/x86/ptrace_syscall_32: Fix no-vDSO segfault 2020-04-17 10:48:40 +02:00
usr initramfs: restore default compression behavior 2020-04-13 10:44:59 +02:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-05 16:42:21 +01:00
.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 MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 16:38:49 +01:00
Makefile Linux 4.19.115 2020-04-13 10:45:17 +02:00
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.