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font: Assign null_font to glyphs in ascii_font_glyph[]

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The calculations in blit_comb() need information from glyph's font, e.g.
grub_font_get_xheight(main_glyph->font). However, main_glyph->font is
NULL if main_glyph comes from ascii_font_glyph[]. Therefore
grub_font_get_*() crashes because of NULL pointer.

There is already a solution, the null_font. So, assign it to those glyphs
in ascii_font_glyph[].

Reported-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Zhang Boyang 2022-10-28 17:29:16 +08:00 committed by Steve McIntyre
parent 918f5efa88
commit b272bbd408
2 changed files with 37 additions and 1 deletions
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36
debian/patches/cve_2022_2601/0013-font-Assign-null_font-to-glyphs-in-ascii_font_glyph.patch vendored Normal file
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@ -0,0 +1,36 @@
From dd539d695482069d28b40f2d3821f710cdcf6ee6 Mon Sep 17 00:00:00 2001
From: Zhang Boyang <zhangboyang.id@gmail.com>
Date: Fri, 28 Oct 2022 17:29:16 +0800
Subject: [PATCH 13/14] font: Assign null_font to glyphs in ascii_font_glyph[]
The calculations in blit_comb() need information from glyph's font, e.g.
grub_font_get_xheight(main_glyph->font). However, main_glyph->font is
NULL if main_glyph comes from ascii_font_glyph[]. Therefore
grub_font_get_*() crashes because of NULL pointer.
There is already a solution, the null_font. So, assign it to those glyphs
in ascii_font_glyph[].
Reported-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
grub-core/font/font.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/grub-core/font/font.c b/grub-core/font/font.c
index cf15dc2f9..3821937e6 100644
--- a/grub-core/font/font.c
+++ b/grub-core/font/font.c
@@ -137,7 +137,7 @@ ascii_glyph_lookup (grub_uint32_t code)
ascii_font_glyph[current]->offset_x = 0;
ascii_font_glyph[current]->offset_y = -2;
ascii_font_glyph[current]->device_width = 8;
- ascii_font_glyph[current]->font = NULL;
+ ascii_font_glyph[current]->font = &null_font;
grub_memcpy (ascii_font_glyph[current]->bitmap,
&ascii_bitmaps[current * ASCII_BITMAP_SIZE],
--
2.30.2

2
grub-core/font/font.c
View File

@ -137,7 +137,7 @@ ascii_glyph_lookup (grub_uint32_t code)
ascii_font_glyph[current]->offset_x = 0;
ascii_font_glyph[current]->offset_y = -2;
ascii_font_glyph[current]->device_width = 8;
ascii_font_glyph[current]->font = NULL;
ascii_font_glyph[current]->font = &null_font;
grub_memcpy (ascii_font_glyph[current]->bitmap,
&ascii_bitmaps[current * ASCII_BITMAP_SIZE],