drm/rockchip: psr: do not dereference encoder before it is null checked.

'encoder' is dereferenced before it is null sanity checked, hence we
potentially have a null pointer dereference bug. Instead, initialise
drm_drv from encoder->dev->dev_private after we are sure 'encoder' is
not null.

Fixes: 5182c1a556d7f ("drm/rockchip: add an common abstracted PSR driver")
Cc: stable@vger.kernel.org
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20181013105654.11827-1-enric.balletbo@collabora.com

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
index 79d00d8..01ff3c8 100644 (file)
--- a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
@@ -189,12 +189,14 @@ EXPORT_SYMBOL(rockchip_drm_psr_flush_all);
 int rockchip_drm_psr_register(struct drm_encoder *encoder,
                        int (*psr_set)(struct drm_encoder *, bool enable))
 {
-       struct rockchip_drm_private *drm_drv = encoder->dev->dev_private;
+       struct rockchip_drm_private *drm_drv;
        struct psr_drv *psr;
 
        if (!encoder || !psr_set)
                return -EINVAL;
 
+       drm_drv = encoder->dev->dev_private;
+
        psr = kzalloc(sizeof(struct psr_drv), GFP_KERNEL);
        if (!psr)
                return -ENOMEM;