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authorNicolai Hähnle <Nicolai.Haehnle@amd.com>2016-12-21 19:46:39 +0100
committerIngo Molnar <mingo@kernel.org>2017-01-14 11:14:53 +0100
commit977625a693283dbb35b2a3f674bc0237f7347348 (patch)
tree19262cc7c358ccd341537d3c2de14cf871feaf7f
parentc516df978df1471793aaa4809b390ecd40fa93c2 (diff)
locking/mutex: Initialize mutex_waiter::ww_ctx with poison when debugging
Help catch cases where mutex_lock is used directly on w/w mutexes, which otherwise result in the w/w tasks reading uninitialized data. Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Maarten Lankhorst <dev@mblankhorst.nl> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dri-devel@lists.freedesktop.org Link: http://lkml.kernel.org/r/1482346000-9927-12-git-send-email-nhaehnle@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--include/linux/poison.h1
-rw-r--r--kernel/locking/mutex.c4
2 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 51334edec506..a39540326417 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 cd8598aa0426..935116723a3d 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -785,6 +785,10 @@ __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);