linux-kernel - [PATCH v1 1/2] driver core: Fix locking bug in deferred_probe_timeout_work

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Message-Id: <20210402040342.2944858-2-saravanak@google.com>
Date:   Thu,  1 Apr 2021 21:03:40 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh@...nel.org>
Cc:     Saravana Kannan <saravanak@...gle.com>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: [PATCH v1 1/2] driver core: Fix locking bug in deferred_probe_timeout_work_func()

list_for_each_entry_safe() is only useful if we are deleting nodes in a
linked list within the loop. It doesn't protect against other threads
adding/deleting nodes to the list in parallel. We need to grab
deferred_probe_mutex when traversing the deferred_probe_pending_list.

Cc: stable@...r.kernel.org
Fixes: 25b4e70dcce9 ("driver core: allow stopping deferred probe after init")
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
 drivers/base/dd.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 20b69b5e0e91..28ad8afd87bc 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -291,14 +291,16 @@ int driver_deferred_probe_check_state(struct device *dev)
 
 static void deferred_probe_timeout_work_func(struct work_struct *work)
 {
-	struct device_private *private, *p;
+	struct device_private *p;
 
 	driver_deferred_probe_timeout = 0;
 	driver_deferred_probe_trigger();
 	flush_work(&deferred_probe_work);
 
-	list_for_each_entry_safe(private, p, &deferred_probe_pending_list, deferred_probe)
-		dev_info(private->device, "deferred probe pending\n");
+	mutex_lock(&deferred_probe_mutex);
+	list_for_each_entry(p, &deferred_probe_pending_list, deferred_probe)
+		dev_info(p->device, "deferred probe pending\n");
+	mutex_unlock(&deferred_probe_mutex);
 	wake_up_all(&probe_timeout_waitqueue);
 }
 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
-- 
2.31.0.208.g409f899ff0-goog