queue-4.14/auxdisplay-ht16k33-fix-potential-user-after-free-on-.patch

   1 From d8c827ab0d2fdd50cb0bcd31b8b1f62a6608fadc Mon Sep 17 00:00:00 2001
   2 From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
   3 Date: Sat, 9 Feb 2019 00:38:45 +0100
   4 Subject: auxdisplay: ht16k33: fix potential user-after-free on module unload
   5
   6 [ Upstream commit 69ef9bc54715fb1cb7786ada15774e469e822209 ]
   7
   8 On module unload/remove, we need to ensure that work does not run
   9 after we have freed resources. Concretely, cancel_delayed_work()
  10 may return while the callback function is still running.
  11
  12 From kernel/workqueue.c:
  13
  14     The work callback function may still be running on return,
  15     unless it returns true and the work doesn't re-arm itself.
  16     Explicitly flush or use cancel_delayed_work_sync() to wait on it.
  17
  18 Link: https://lore.kernel.org/lkml/20190204220952.30761-1-TheSven73@googlemail.com/
  19 Reported-by: Sven Van Asbroeck <thesven73@gmail.com>
  20 Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
  21 Reviewed-by: Sven Van Asbroeck <TheSven73@gmail.com>
  22 Acked-by: Robin van der Gracht <robin@protonic.nl>
  23 Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
  24 Signed-off-by: Sasha Levin <sashal@kernel.org>
  25 ---
  26  drivers/auxdisplay/ht16k33.c | 2 +-
  27  1 file changed, 1 insertion(+), 1 deletion(-)
  28
  29 diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
  30 index fbfa5b4cc567..a93ded300740 100644
  31 --- a/drivers/auxdisplay/ht16k33.c
  32 +++ b/drivers/auxdisplay/ht16k33.c
  33 @@ -517,7 +517,7 @@ static int ht16k33_remove(struct i2c_client *client)
  34         struct ht16k33_priv *priv = i2c_get_clientdata(client);
  35         struct ht16k33_fbdev *fbdev = &priv->fbdev;
  36
  37 -       cancel_delayed_work(&fbdev->work);
  38 +       cancel_delayed_work_sync(&fbdev->work);
  39         unregister_framebuffer(fbdev->info);
  40         framebuffer_release(fbdev->info);
  41         free_page((unsigned long) fbdev->buffer);
  42 --
  43 2.19.1
  44