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Subject[tip:locking/core] locking/mutex: Test for initialized mutex
Commit-ID:  6c11c6e3d5e9e5caf8686cd6a5e4552cfc3ea326
Gitweb: https://git.kernel.org/tip/6c11c6e3d5e9e5caf8686cd6a5e4552cfc3ea326
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 3 Jul 2019 11:21:26 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 25 Jul 2019 15:39:27 +0200

locking/mutex: Test for initialized mutex

An uninitialized/ zeroed mutex will go unnoticed because there is no
check for it. There is a magic check in the unlock's slowpath path which
might go unnoticed if the unlock happens in the fastpath.

Add a ->magic check early in the mutex_lock() and mutex_trylock() path.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190703092125.lsdf4gpsh2plhavb@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/mutex.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index edd1c082dbf5..5e069734363c 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -908,6 +908,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,

might_sleep();

+#ifdef CONFIG_DEBUG_MUTEXES
+ DEBUG_LOCKS_WARN_ON(lock->magic != lock);
+#endif
+
ww = container_of(lock, struct ww_mutex, base);
if (use_ww_ctx && ww_ctx) {
if (unlikely(ww_ctx == READ_ONCE(ww->ctx)))
@@ -1379,8 +1383,13 @@ __ww_mutex_lock_interruptible_slowpath(struct ww_mutex *lock,
*/
int __sched mutex_trylock(struct mutex *lock)
{
- bool locked = __mutex_trylock(lock);
+ bool locked;
+
+#ifdef CONFIG_DEBUG_MUTEXES
+ DEBUG_LOCKS_WARN_ON(lock->magic != lock);
+#endif

+ locked = __mutex_trylock(lock);
if (locked)
mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);

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