linux-kernel - [PATCH v2 2/2] drm/sun4i: tcon: prevent tcon->panel dereference if null

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Date:   Wed,  3 Oct 2018 16:24:58 +0200
From:   Giulio Benetti <giulio.benetti@...ronovasrl.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Giulio Benetti <giulio.benetti@...ronovasrl.com>
Subject: [PATCH v2 2/2] drm/sun4i: tcon: prevent tcon->panel dereference if null

If using tcon with VGA, tcon->panel will be null(0), this will cause
segmentation fault when trying to dereference tcon->panel->connector.

Add tcon->panel null check before calling
sun4i_tcon0_mode_set_dithering().

Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
Fixes: f11adcecbd5f ("drm/sun4i: tcon: Add dithering support for
                      RGB565/RGB666 LCD panels")
Reviewed-by: Chen-Yu Tsai <wens@...e.org>
---
Changes V1->V2:
* none

 drivers/gpu/drm/sun4i/sun4i_tcon.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index e4b3bd0307ef..f949287d926c 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -491,7 +491,8 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 	sun4i_tcon0_mode_set_common(tcon, mode);
 
 	/* Set dithering if needed */
-	sun4i_tcon0_mode_set_dithering(tcon, tcon->panel->connector);
+	if (tcon->panel)
+		sun4i_tcon0_mode_set_dithering(tcon, tcon->panel->connector);
 
 	/* Adjust clock delay */
 	clk_delay = sun4i_tcon_get_clk_delay(mode, 0);
-- 
2.17.1