From: Nicolai Hähnle <Nicolai.Haehnle@xxxxxxx>
Help catch cases where mutex_lock is used directly on w/w mutexes, which
otherwise result in the w/w tasks reading uninitialized data.
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Maarten Lankhorst <dev@xxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel@xxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@xxxxxxx>
---
include/linux/poison.h | 1 +
kernel/locking/mutex.c | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 51334ed..a395403 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -80,6 +80,7 @@
/********** kernel/mutexes **********/
#define MUTEX_DEBUG_INIT 0x11
#define MUTEX_DEBUG_FREE 0x22
+#define MUTEX_POISON_WW_CTX ((void *) 0x500 + POISON_POINTER_DELTA)
/********** lib/flex_array.c **********/
#define FLEX_ARRAY_FREE 0x6c /* for use-after-free poisoning */
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 0bafb37..3e46a12 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -791,6 +791,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
if (!use_ww_ctx) {
/* add waiting tasks to the end of the waitqueue (FIFO): */
list_add_tail(&waiter.list, &lock->wait_list);
+
+#ifdef CONFIG_DEBUG_MUTEXES
+ waiter.ww_ctx = MUTEX_POISON_WW_CTX;
+#endif
} else {
/* Add in stamp order, waking up waiters that must back off. */
ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);
--
2.7.4
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