forge/linux-uconsole
1
0
Fork 0
Code Issues 1 Pull requests Projects Releases Packages Wiki Activity Actions

locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps()

Browse source 
[ 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>
This commit is contained in:
Boqun Feng 2020-03-12 23:12:55 +08:00 • committed by Greg Kroah-Hartman
commit c6090fe788
1 changed files with 4 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

4
kernel/locking/lockdep.c
View file

@ -1260,9 +1260,11 @@ unsigned long lockdep_count_forward_deps(struct lock_class *class)
this.class = class;
raw_local_irq_save(flags);
current->lockdep_recursion = 1;
arch_spin_lock(&lockdep_lock);
ret = __lockdep_count_forward_deps(&this);
arch_spin_unlock(&lockdep_lock);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
return ret;
@ -1287,9 +1289,11 @@ unsigned long lockdep_count_backward_deps(struct lock_class *class)
this.class = class;
raw_local_irq_save(flags);
current->lockdep_recursion = 1;
arch_spin_lock(&lockdep_lock);
ret = __lockdep_count_backward_deps(&this);
arch_spin_unlock(&lockdep_lock);
current->lockdep_recursion = 0;
raw_local_irq_restore(flags);
return ret;