linux-kernel - [PATCH 5.4 14/18] driver core: Fix locking bug in deferred_probe_timeout_work

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Message-Id: <20210415144413.500053438@linuxfoundation.org>
Date:   Thu, 15 Apr 2021 16:48:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Saravana Kannan <saravanak@...gle.com>
Subject: [PATCH 5.4 14/18] driver core: Fix locking bug in deferred_probe_timeout_work_func()

From: Saravana Kannan <saravanak@...gle.com>

commit eed6e41813deb9ee622cd9242341f21430d7789f upstream.

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>
Link: https://lore.kernel.org/r/20210402040342.2944858-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/base/dd.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -300,14 +300,16 @@ int driver_deferred_probe_check_state_co
 
 static void deferred_probe_timeout_work_func(struct work_struct *work)
 {
-	struct device_private *private, *p;
+	struct device_private *p;
 
 	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");
+	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);
 }
 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);