linux-kernel - Re: general protection fault in lockdep_invariant

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Date:   Wed, 8 Nov 2017 09:40:31 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot 
        <bot+2e39c7a45268c036c9e90433a48c9dd550276dc6@...kaller.appspotmail.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, syzkaller-bugs@...glegroups.com
Subject: Re: general protection fault in lockdep_invariant_state (2)

On Wed, Nov 08, 2017 at 09:19:53AM +0100, Dmitry Vyukov wrote:

> > R13: 0000000000402260 R14: 00000000004022f0 R15: 0000000000000000
> > kasan: CONFIG_KASAN_INLINE enabled
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] SMP KASAN
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > Modules linked in:
> > CPU: 3 PID: 2982 Comm: syzkaller521009 Not tainted 4.14.0-rc7-next-20171103+
> > #10
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> > task: ffff88003d6b25c0 task.stack: ffff88003abd0000
> > RIP: 0010:invalidate_xhlock kernel/locking/lockdep.c:4719 [inline]
> > RIP: 0010:lockdep_invariant_state+0xd6/0x120 kernel/locking/lockdep.c:4793


Does this help?

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index db933d063bfc..da2904418599 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4793,7 +4793,8 @@ 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)