linux-kernel - [PATCH 5/6] drm/panic: Fix divide by 0 if the screen width

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Message-ID: <20251009122955.562888-6-jfalempe@redhat.com>
Date: Thu,  9 Oct 2025 14:24:52 +0200
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Jocelyn Falempe <jfalempe@...hat.com>,
	Javier Martinez Canillas <javierm@...hat.com>,
	linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Cc: stable@...r.kernel.org
Subject: [PATCH 5/6] drm/panic: Fix divide by 0 if the screen width < font width

In the unlikely case that the screen is tiny, and smaller than the
font width, it leads to a divide by 0:

draw_line_with_wrap()
chars_per_row = sb->width / font->width = 0
line_wrap.len = line->len % chars_per_row;

This will trigger a divide by 0

Signed-off-by: Jocelyn Falempe <jfalempe@...hat.com>
---
 drivers/gpu/drm/drm_panic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
index 69be9d835ccf..bc5158683b2b 100644
--- a/drivers/gpu/drm/drm_panic.c
+++ b/drivers/gpu/drm/drm_panic.c
@@ -523,7 +523,7 @@ static void draw_panic_static_kmsg(struct drm_scanout_buffer *sb)
 	struct drm_panic_line line;
 	int yoffset;
 
-	if (!font)
+	if (!font || font->width > sb->width)
 		return;
 
 	yoffset = sb->height - font->height - (sb->height % font->height) / 2;
-- 
2.51.0