[PATCH 1/2] Fonts: Support FONT_EXTRA_WORDS macros for font_6x8

From: Peilin Ye
Date: Sun Oct 18 2020 - 14:13:55 EST


Recently, in commit 6735b4632def ("Fonts: Support FONT_EXTRA_WORDS macros
for built-in fonts"), we wrapped each of our built-in data buffers in a
`font_data` structure, in order to use the following macros on them, see
include/linux/font.h:

#define REFCOUNT(fd) (((int *)(fd))[-1])
#define FNTSIZE(fd) (((int *)(fd))[-2])
#define FNTCHARCNT(fd) (((int *)(fd))[-3])
#define FNTSUM(fd) (((int *)(fd))[-4])

#define FONT_EXTRA_WORDS 4

Do the same thing to our new 6x8 font. For built-in fonts, currently we
only use FNTSIZE(). Since this is only a temporary solution for an
out-of-bounds issue in the framebuffer layer (see commit 5af08640795b
("fbcon: Fix global-out-of-bounds read in fbcon_get_font()")), all the
three other fields are intentionally set to zero in order to discourage
using these negative-indexing macros.

Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
---
lib/fonts/font_6x8.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/fonts/font_6x8.c b/lib/fonts/font_6x8.c
index e06447788418..700039a9ceae 100644
--- a/lib/fonts/font_6x8.c
+++ b/lib/fonts/font_6x8.c
@@ -3,8 +3,8 @@

#define FONTDATAMAX 2048

-static const unsigned char fontdata_6x8[FONTDATAMAX] = {
-
+static struct font_data fontdata_6x8 = {
+ { 0, 0, FONTDATAMAX, 0 }, {
/* 0 0x00 '^@' */
0x00, /* 000000 */
0x00, /* 000000 */
@@ -2564,13 +2564,13 @@ static const unsigned char fontdata_6x8[FONTDATAMAX] = {
0x00, /* 000000 */
0x00, /* 000000 */
0x00, /* 000000 */
-};
+} };

const struct font_desc font_6x8 = {
.idx = FONT6x8_IDX,
.name = "6x8",
.width = 6,
.height = 8,
- .data = fontdata_6x8,
+ .data = fontdata_6x8.data,
.pref = 0,
};
--
2.25.1