linux-kernel - [PATCH/RFC 3/8] drm/ssd130x: Bail out early if data

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Date:   Thu, 13 Jul 2023 15:17:11 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Javier Martinez Canillas <javierm@...hat.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH/RFC 3/8] drm/ssd130x: Bail out early if data_array is not yet available

Calling ssd130x_buf_alloc() from ssd130x_encoder_helper_atomic_enable()
is too late, causing a NULL pointer dereference:

    ssd130x_update_rect.isra.0+0x13c/0x340
    ssd130x_primary_plane_helper_atomic_update+0x26c/0x284
    drm_atomic_helper_commit_planes+0xfc/0x27c

Work around that by checking if data_array is valid.

Obviously this needs a better fix...

Fixes: 49d7d581ceaf4cf8 ("drm/ssd130x: Don't allocate buffers on each plane update")
Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
---
 drivers/gpu/drm/solomon/ssd130x.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c
index b4c376962629580b..8ef5f61854fd7340 100644
--- a/drivers/gpu/drm/solomon/ssd130x.c
+++ b/drivers/gpu/drm/solomon/ssd130x.c
@@ -481,6 +481,7 @@ static int ssd130x_update_rect(struct ssd130x_device *ssd130x, struct drm_rect *
 	u32 array_idx = 0;
 	int ret, i, j, k;
 
+if (!data_array) { pr_info("%s: data_array not yet initialized\n", __func__); return 0; }
 	drm_WARN_ONCE(drm, y % 8 != 0, "y must be aligned to screen page\n");
 
 	/*
-- 
2.34.1