diff mbox series

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

Message ID 20181003142458.33120-2-giulio.benetti@micronovasrl.com (mailing list archive)
State New, archived
Headers show
Series [v2,1/2] drm/sun4i: tcon: fix check of tcon->panel null pointer | expand

Commit Message

Giulio Benetti Oct. 3, 2018, 2:24 p.m. UTC 
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@micronovasrl.com>
Fixes: f11adcecbd5f ("drm/sun4i: tcon: Add dithering support for
                      RGB565/RGB666 LCD panels")
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
---
Changes V1->V2:
* none

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

Comments

Maxime Ripard Oct. 4, 2018, 7:56 p.m. UTC | #1 
On Wed, Oct 03, 2018 at 04:24:58PM +0200, Giulio Benetti wrote:
> If using tcon with VGA,

We don't have support for VGA at the moment. Or are you talking about
using a VGA bridge?

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

It's not a segmentation fault, but a null pointer dereference. And
that case will also happen with bridges.

Maxime
Giulio Benetti Oct. 5, 2018, 9:38 p.m. UTC | #2 
Hi,

Il 04/10/2018 21:56, Maxime Ripard ha scritto:
> On Wed, Oct 03, 2018 at 04:24:58PM +0200, Giulio Benetti wrote:
>> If using tcon with VGA,
> 
> We don't have support for VGA at the moment. Or are you talking about
> using a VGA bridge?

You're right, in general VGA is not the point.
tcon->panel is retrieved by drm_of_find_panel_or_bridge() and panel can 
be present or not.

>> tcon->panel will be null(0), this will cause segmentation fault when
>> trying to dereference tcon->panel->connector.
> 
> It's not a segmentation fault, but a null pointer dereference. And
> that case will also happen with bridges.

Right.

Going to improve/rewrite commit logs and submit v2 patchset.

Thanks for reviewing.

Best regards
diff mbox series

Patch

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);