[PATCH v2 3/3] drm/panic: Add a kmsg panic screen

[Dan Carpenter]

Hi Jocelyn,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Jocelyn-Falempe/drm-panic-only-draw-the-foreground-color-in-drm_panic_blit/20240603-181247
base:   86266829ea755f737762ebda614c59b136c8feac
patch link:    https://lore.kernel.org/r/20240603095343.39588-4-jfalempe%40redhat.com
patch subject: [PATCH v2 3/3] drm/panic: Add a kmsg panic screen
config: i386-randconfig-141-20240604 (https://download.01.org/0day-ci/archive/20240604/202406041051.KuVqtZCd-lkp@intel.com/config)
compiler: gcc-13 (Ubuntu 13.2.0-4ubuntu3) 13.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp at intel.com>
| Reported-by: Dan Carpenter <dan.carpenter at linaro.org>
| Closes: https://lore.kernel.org/r/202406041051.KuVqtZCd-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/drm_panic.c:531 draw_panic_static_kmsg() warn: variable dereferenced before check 'font' (see line 529)

vim +/font +531 drivers/gpu/drm/drm_panic.c

c259bba1e69ff2 Jocelyn Falempe 2024-06-03  519  static void draw_panic_static_kmsg(struct drm_scanout_buffer *sb)
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  520  {
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  521  	u32 fg_color = convert_from_xrgb8888(CONFIG_DRM_PANIC_FOREGROUND_COLOR, sb->format->format);
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  522  	u32 bg_color = convert_from_xrgb8888(CONFIG_DRM_PANIC_BACKGROUND_COLOR, sb->format->format);
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  523  	const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  524  	struct drm_rect r_screen = DRM_RECT_INIT(0, 0, sb->width, sb->height);
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  525  	struct kmsg_dump_iter iter;
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  526  	char kmsg_buf[512];
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  527  	size_t kmsg_len;
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  528  	struct drm_panic_line line;
c259bba1e69ff2 Jocelyn Falempe 2024-06-03 @529  	int yoffset = sb->height - font->height - (sb->height % font->height) / 2;
                                                                                   ^^^^^^^^^^^^                 ^^^^^^^^^^^^
Unchecked dereferences

c259bba1e69ff2 Jocelyn Falempe 2024-06-03  530  
c259bba1e69ff2 Jocelyn Falempe 2024-06-03 @531  	if (!font)
                                                             ^^^^
Checked too late

c259bba1e69ff2 Jocelyn Falempe 2024-06-03  532  		return;
c259bba1e69ff2 Jocelyn Falempe 2024-06-03  533  

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