From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 6 Dec 2017 16:32:47 +0000 (+0100)
Subject: locking/lockdep: Fix possible NULL deref
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5e351ad106997e06b2dc3da9c6b939b95f67fb88;p=linux.git

locking/lockdep: Fix possible NULL deref

We can't invalidate xhlocks when we've not yet allocated any.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: f52be5708076 ("locking/lockdep: Untangle xhlock history save/restore from task independence")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 9776da8db180d..670d8d7d8087c 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4790,7 +4790,8 @@ void lockdep_invariant_state(bool force)
 	 * Verify the former, enforce the latter.
 	 */
 	WARN_ON_ONCE(!force && current->lockdep_depth);
-	invalidate_xhlock(&xhlock(current->xhlock_idx));
+	if (current->xhlocks)
+		invalidate_xhlock(&xhlock(current->xhlock_idx));
 }
 
 static int cross_lock(struct lockdep_map *lock)