linux-kernel - [PATCH 2/7] drm/sun4i: dw-hdmi: Remove double encoder cleanup

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Message-ID: <20230924192604.3262187-3-jernej.skrabec@gmail.com>
Date:   Sun, 24 Sep 2023 21:25:59 +0200
From:   Jernej Skrabec <jernej.skrabec@...il.com>
To:     mripard@...nel.org, wens@...e.org
Cc:     airlied@...il.com, daniel@...ll.ch, samuel@...lland.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Jernej Skrabec <jernej.skrabec@...il.com>
Subject: [PATCH 2/7] drm/sun4i: dw-hdmi: Remove double encoder cleanup

It turns out that comment is wrong - dw hdmi driver never does any
encoder cleanup. In fact, cleanup is done automatically, in destroy
callback of encoder. Even more, encoder memory will be freed when hdmi
device is destroyed. However, encoder will be cleaned up after that, in
drm_mode_config_cleanup(), which is called later. This will cause use
after free bug.

Remove redundant encoder cleanup, switch memory allocation to live as
long as drm object and while at it, check return code of encoder
initialization.

Fixes: b7c7436a5ff0 ("drm/sun4i: Implement A83T HDMI driver")
Signed-off-by: Jernej Skrabec <jernej.skrabec@...il.com>
---
 drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
index 0b647b030b15..8f8d3bdba5ce 100644
--- a/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
+++ b/drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c
@@ -8,6 +8,7 @@
 #include <linux/of.h>
 #include <linux/platform_device.h>
 
+#include <drm/drm_managed.h>
 #include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_of.h>
 #include <drm/drm_simple_kms_helper.h>
@@ -107,7 +108,7 @@ static int sun8i_dw_hdmi_bind(struct device *dev, struct device *master,
 	if (!pdev->dev.of_node)
 		return -ENODEV;
 
-	hdmi = devm_kzalloc(&pdev->dev, sizeof(*hdmi), GFP_KERNEL);
+	hdmi = drmm_kzalloc(drm, sizeof(*hdmi), GFP_KERNEL);
 	if (!hdmi)
 		return -ENOMEM;
 
@@ -180,7 +181,9 @@ static int sun8i_dw_hdmi_bind(struct device *dev, struct device *master,
 		goto err_disable_clk_tmds;
 
 	drm_encoder_helper_add(encoder, &sun8i_dw_hdmi_encoder_helper_funcs);
-	drm_simple_encoder_init(drm, encoder, DRM_MODE_ENCODER_TMDS);
+	ret = drm_simple_encoder_init(drm, encoder, DRM_MODE_ENCODER_TMDS);
+	if (ret)
+		goto err_deinit_phy;
 
 	plat_data->mode_valid = hdmi->quirks->mode_valid;
 	plat_data->use_drm_infoframe = hdmi->quirks->use_drm_infoframe;
@@ -189,20 +192,14 @@ static int sun8i_dw_hdmi_bind(struct device *dev, struct device *master,
 	platform_set_drvdata(pdev, hdmi);
 
 	hdmi->hdmi = dw_hdmi_bind(pdev, encoder, plat_data);
-
-	/*
-	 * If dw_hdmi_bind() fails we'll never call dw_hdmi_unbind(),
-	 * which would have called the encoder cleanup.  Do it manually.
-	 */
 	if (IS_ERR(hdmi->hdmi)) {
 		ret = PTR_ERR(hdmi->hdmi);
-		goto cleanup_encoder;
+		goto err_deinit_phy;
 	}
 
 	return 0;
 
-cleanup_encoder:
-	drm_encoder_cleanup(encoder);
+err_deinit_phy:
 	sun8i_hdmi_phy_deinit(hdmi->phy);
 err_disable_clk_tmds:
 	clk_disable_unprepare(hdmi->clk_tmds);
-- 
2.42.0