[PATCH 2/6] drm/rockchip: dw_dp: Switch to drmm_kzalloc()

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

Driver makes use of drmm_encoder_init() to initialize the encoder and
automatically handle the cleanup by registering drm_encoder_cleanup()
with drmm_add_action().

However, the internal structure containing the encoder part gets
allocated with devm_kzalloc(), which happens while component_bind_all()
is being called from Rockchip DRM driver.  The component framework
further ensures it is deallocated as part of releasing all the resources
claimed during bind, which is triggered from component_unbind_all().

When the reference to the DRM device gets eventually dropped via
drm_dev_put() in rockchip_drm_unbind(), drmm_encoder_alloc_release()
attempts to access the now released encoder structure, leading to
use-after-free.

Ensure driver's internal structure is still reachable on encoder cleanup
by switching from a device-managed allocation to a drm-managed one.

Fixes: d68ba7bac955 ("drm/rockchip: Add RK3588 DPTX output support")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
 drivers/gpu/drm/rockchip/dw_dp-rockchip.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/dw_dp-rockchip.c b/drivers/gpu/drm/rockchip/dw_dp-rockchip.c
index 25ab4e46301e..98d97e0f3cf4 100644
--- a/drivers/gpu/drm/rockchip/dw_dp-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_dp-rockchip.c
@@ -13,6 +13,7 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_bridge.h>
 #include <drm/drm_bridge_connector.h>
+#include <drm/drm_managed.h>
 #include <drm/drm_of.h>
 #include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
@@ -82,7 +83,7 @@ static int dw_dp_rockchip_bind(struct device *dev, struct device *master, void *
 	struct drm_connector *connector;
 	int ret;
 
-	dp = devm_kzalloc(dev, sizeof(*dp), GFP_KERNEL);
+	dp = drmm_kzalloc(drm_dev, sizeof(*dp), GFP_KERNEL);
 	if (!dp)
 		return -ENOMEM;
 

-- 
2.52.0