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authorBoqun Feng <boqun.feng@gmail.com>2020-03-12 16:12:55 +0100
committerPeter Zijlstra <peterz@infradead.org>2020-03-20 13:06:25 +0100
commit25016bd7f4caf5fc983bbab7403d08e64cba3004 (patch)
treed79ed47688ae18f1e52a6e102d79ec55775ac92f /kernel/locking
parentasm-generic/bitops: Update stale comment (diff)
downloadlinux-25016bd7f4caf5fc983bbab7403d08e64cba3004.tar.xz
linux-25016bd7f4caf5fc983bbab7403d08e64cba3004.zip
locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps()
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
Diffstat (limited to 'kernel/locking')
-rw-r--r--kernel/locking/lockdep.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e55c4ee14e64..2564950a402c 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1723,9 +1723,11 @@ 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;
@@ -1750,9 +1752,11 @@ 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;