On Sun, May 28, 2017 at 07:16:55PM +0200, Hans de Goede wrote:
> Since commit a39be606f99d ("drm: Do a full device unregister when
> unplugging") drm_unplug_dev has been calling drm_dev_unregister followed
> by a drm_put_dev when open_count reaches 0. This drm_put_dev calls
> drm_dev_unregister again. Since drm_dev_unregister is not protected
> against being called multiple times this leads to havoc.
>
> This commit fixes this by calling drm_dev_unref instead of drm_put_dev.
>
> Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Marco Diego Aurélio Mesquita <marcodiegomesquita@xxxxxxxxx>
> Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@xxxxxxxxx>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> Note I don't have any USB display devices at hand for testing atm so
> this patch has only been compile tested.
> ---
> Changes in v2:
> -Remove unnecessary mutex changes
Offending patch is in 4.8 ... do we need cc: stable? Does this need a
bugreport link?
-Daniel
> ---
> drivers/gpu/drm/drm_drv.c | 6 +++---
> drivers/gpu/drm/drm_file.c | 2 +-
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index b5c6bb46a425..30b5382bf877 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -364,9 +364,9 @@ void drm_unplug_dev(struct drm_device *dev)
>
> drm_device_set_unplugged(dev);
>
> - if (dev->open_count == 0) {
> - drm_put_dev(dev);
> - }
> + if (dev->open_count == 0)
> + drm_dev_unref(dev);
> +
> mutex_unlock(&drm_global_mutex);
> }
> EXPORT_SYMBOL(drm_unplug_dev);
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index 3783b659cd38..edba71c8ccc3 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -424,7 +424,7 @@ int drm_release(struct inode *inode, struct file *filp)
> if (!--dev->open_count) {
> drm_lastclose(dev);
> if (drm_device_is_unplugged(dev))
> - drm_put_dev(dev);
> + drm_dev_unref(dev);
> }
> mutex_unlock(&drm_global_mutex);
>
> --
> 2.13.0
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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