linux-kernel - [PATCH 4.14 117/159] locking/lockdep: Fix possible NULL deref

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Date:   Fri, 23 Feb 2018 19:27:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 117/159] locking/lockdep: Fix possible NULL deref

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@...radead.org>


[ Upstream commit 5e351ad106997e06b2dc3da9c6b939b95f67fb88 ]

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

Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Fixes: f52be5708076 ("locking/lockdep: Untangle xhlock history save/restore from task independence")
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/locking/lockdep.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4777,7 +4777,8 @@ 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)