linux-kernel - [PATCH 4.19 110/148] driver core: Add missing dev->bus->need_parent

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Date:   Fri, 11 Jan 2019 15:14:48 +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,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [PATCH 4.19 110/148] driver core: Add missing dev->bus->need_parent_lock checks

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

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

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

commit e121a833745b4708b660e3fe6776129c2956b041 upstream.

__device_release_driver() has to check dev->bus->need_parent_lock
before dropping the parent lock and acquiring it again as it may
attempt to drop a lock that hasn't been acquired or lock a device
that shouldn't be locked and create a lock imbalance.

Fixes: 8c97a46af04b (driver core: hold dev's parent lock when needed)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: stable <stable@...r.kernel.org>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/base/dd.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -931,11 +931,11 @@ static void __device_release_driver(stru

 		while (device_links_busy(dev)) {
 			device_unlock(dev);
-			if (parent)
+			if (parent && dev->bus->need_parent_lock)
 				device_unlock(parent);

 			device_links_unbind_consumers(dev);
-			if (parent)
+			if (parent && dev->bus->need_parent_lock)
 				device_lock(parent);

 			device_lock(dev);