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 9776da8..670d8d7 100644 (file)
--- 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)