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    Subject[PATCH 5.4 14/18] driver core: Fix locking bug in deferred_probe_timeout_work_func()
    Date
    From: Saravana Kannan <saravanak@google.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@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>

    ---
    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);


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