drm/drv: Hold ref on parent device during drm_device lifetime

BugLink: https://bugs.launchpad.net/bugs/1837517
[ Upstream commit 56be6503aab2bc3a30beae408071b9be5e1bae51 ]

This makes it safe to access drm_device->dev after the parent device has
been removed/unplugged.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190225144232.20761-2-noralf@tronnes.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 7a59b8b3ed5a40e49f0b57a45d671e009451e2de..81c8936bc1d3c19b0807dbc7334ab9aeddc9628c 100644 (file)
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -499,7 +499,7 @@ int drm_dev_init(struct drm_device *dev,
        BUG_ON(!parent);
 
        kref_init(&dev->ref);
-       dev->dev = parent;
+       dev->dev = get_device(parent);
        dev->driver = driver;
 
        /* no per-device feature limits by default */
@@ -569,6 +569,7 @@ err_minors:
        drm_minor_free(dev, DRM_MINOR_RENDER);
        drm_fs_inode_free(dev->anon_inode);
 err_free:
+       put_device(dev->dev);
        mutex_destroy(&dev->master_mutex);
        mutex_destroy(&dev->ctxlist_mutex);
        mutex_destroy(&dev->clientlist_mutex);
@@ -604,6 +605,8 @@ void drm_dev_fini(struct drm_device *dev)
        drm_minor_free(dev, DRM_MINOR_PRIMARY);
        drm_minor_free(dev, DRM_MINOR_RENDER);
 
+       put_device(dev->dev);
+
        mutex_destroy(&dev->master_mutex);
        mutex_destroy(&dev->ctxlist_mutex);
        mutex_destroy(&dev->clientlist_mutex);