linux-kernel - [PATCH 4.4 27/53] drm: rcar-du: Fix crash in encoder failure error path

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Date:   Mon, 28 Aug 2017 10:05:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
        Thong Ho <thong.ho.px@....renesas.com>,
        Nhan Nguyen <nhan.nguyen.yb@...esas.com>
Subject: [PATCH 4.4 27/53] drm: rcar-du: Fix crash in encoder failure error path

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

commit 05ee29e94acf0d4b3998c3f93374952de8f90176 upstream.

When an encoder fails to initialize the driver prints an error message
to the kernel log. The message contains the name of the encoder's DT
node, which is NULL for internal encoders. Use the of_node_full_name()
macro to avoid dereferencing a NULL pointer, print the output number to
add more context to the error, and make sure we still own a reference to
the encoder's DT node by delaying the of_node_put() call.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
Signed-off-by: Thong Ho <thong.ho.px@....renesas.com>
Signed-off-by: Nhan Nguyen <nhan.nguyen.yb@...esas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/rcar-du/rcar_du_kms.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
+++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
@@ -642,13 +642,13 @@ static int rcar_du_encoders_init_one(str
 	}
 
 	ret = rcar_du_encoder_init(rcdu, enc_type, output, encoder, connector);
-	of_node_put(encoder);
-	of_node_put(connector);
-
 	if (ret && ret != -EPROBE_DEFER)
 		dev_warn(rcdu->dev,
-			 "failed to initialize encoder %s (%d), skipping\n",
-			 encoder->full_name, ret);
+			 "failed to initialize encoder %s on output %u (%d), skipping\n",
+			 of_node_full_name(encoder), output, ret);
+
+	of_node_put(encoder);
+	of_node_put(connector);
 
 	return ret;
 }