Patch "locking/lockdep: Add nest_lock integrity test" has been added to the 4.4-stable tree

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This is a note to let you know that I've just added the patch titled

    locking/lockdep: Add nest_lock integrity test

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     locking-lockdep-add-nest_lock-integrity-test.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From foo@baz Thu Oct 19 15:15:46 CEST 2017
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Wed, 1 Mar 2017 16:23:30 +0100
Subject: locking/lockdep: Add nest_lock integrity test

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>


[ Upstream commit 7fb4a2cea6b18dab56d609530d077f168169ed6b ]

Boqun reported that hlock->references can overflow. Add a debug test
for that to generate a clear error when this happens.

Without this, lockdep is likely to report a mysterious failure on
unlock.

Reported-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Nicolai Hähnle <Nicolai.Haehnle@xxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/locking/lockdep.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3128,10 +3128,17 @@ static int __lock_acquire(struct lockdep
 	if (depth) {
 		hlock = curr->held_locks + depth - 1;
 		if (hlock->class_idx == class_idx && nest_lock) {
-			if (hlock->references)
+			if (hlock->references) {
+				/*
+				 * Check: unsigned int references:12, overflow.
+				 */
+				if (DEBUG_LOCKS_WARN_ON(hlock->references == (1 << 12)-1))
+					return 0;
+
 				hlock->references++;
-			else
+			} else {
 				hlock->references = 2;
+			}
 
 			return 1;
 		}


Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are

queue-4.4/percpu-make-this_cpu_generic_read-atomic-w.r.t.-interrupts.patch
queue-4.4/locking-lockdep-add-nest_lock-integrity-test.patch



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