FAILED: patch "[PATCH] driver core: Fix locking bug in" failed to apply to 4.19-stable tree

FAILED: patch "[PATCH] driver core: Fix locking bug in" failed to apply to 4.19-stable tree

[gregkh]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From eed6e41813deb9ee622cd9242341f21430d7789f Mon Sep 17 00:00:00 2001
From: Saravana Kannan <saravanak@google.com>
Date: Thu, 1 Apr 2021 21:03:40 -0700
Subject: [PATCH] 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@vger.kernel.org
Fixes: 25b4e70dcce9 ("driver core: allow stopping deferred probe after init")
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20210402040342.2944858-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index e2cf3b29123e..37a5e5f8b221 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -292,14 +292,16 @@ 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);

Re: FAILED: patch "[PATCH] driver core: Fix locking bug in" failed to apply to 4.19-stable tree

[Saravana Kannan]

On Sun, Apr 11, 2021 at 12:23 AM <gregkh@linuxfoundation.org> wrote:
>
>
> The patch below does not apply to the 4.19-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

I sent a patch that should resolve the conflict for 4.19 and 5.4.
https://lore.kernel.org/lkml/20210412180907.1980874-1-saravanak@google.com/T/#u

-Saravana

>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From eed6e41813deb9ee622cd9242341f21430d7789f Mon Sep 17 00:00:00 2001
> From: Saravana Kannan <saravanak@google.com>
> Date: Thu, 1 Apr 2021 21:03:40 -0700
> Subject: [PATCH] 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@vger.kernel.org
> Fixes: 25b4e70dcce9 ("driver core: allow stopping deferred probe after init")
> Signed-off-by: Saravana Kannan <saravanak@google.com>
> Link: https://lore.kernel.org/r/20210402040342.2944858-2-saravanak@google.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index e2cf3b29123e..37a5e5f8b221 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -292,14 +292,16 @@ 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);
>