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authorPeilin Ye <yepeilin.cs@gmail.com>2020-09-24 16:42:22 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-10-14 10:51:10 +0300
commit2832691e0106b31823b0b1ca51f6f7ba34875279 (patch)
tree17717f9abb057c0d2ab9c043e1f5007da1a5bfea /lib/fonts/font_8x16.c
parent052841a35d32c4c3084e07749cdd5c6b412d6ed2 (diff)
downloadlinux-2832691e0106b31823b0b1ca51f6f7ba34875279.tar.xz
Fonts: Support FONT_EXTRA_WORDS macros for built-in fonts
commit 6735b4632def0640dbdf4eb9f99816aca18c4f16 upstream. syzbot has reported an issue in the framebuffer layer, where a malicious user may overflow our built-in font data buffers. In order to perform a reliable range check, subsystems need to know `FONTDATAMAX` for each built-in font. Unfortunately, our font descriptor, `struct console_font` does not contain `FONTDATAMAX`, and is part of the UAPI, making it infeasible to modify it. For user-provided fonts, the framebuffer layer resolves this issue by reserving four extra words at the beginning of data buffers. Later, whenever a function needs to access them, it simply uses the following macros: Recently we have gathered all the above macros to <linux/font.h>. Let us do the same thing for built-in fonts, prepend four extra words (including `FONTDATAMAX`) to their data buffers, so that subsystems can use these macros for all fonts, no matter built-in or user-provided. This patch depends on patch "fbdev, newport_con: Move FONT_EXTRA_WORDS macros into linux/font.h". Cc: stable@vger.kernel.org Link: https://syzkaller.appspot.com/bug?id=08b8be45afea11888776f897895aef9ad1c3ecfd Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/ef18af00c35fb3cc826048a5f70924ed6ddce95b.1600953813.git.yepeilin.cs@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib/fonts/font_8x16.c')
-rw-r--r--lib/fonts/font_8x16.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/lib/fonts/font_8x16.c b/lib/fonts/font_8x16.c
index 34292cdfaa23..b7ae913e5b79 100644
--- a/lib/fonts/font_8x16.c
+++ b/lib/fonts/font_8x16.c
@@ -10,8 +10,8 @@
#define FONTDATAMAX 4096
-static const unsigned char fontdata_8x16[FONTDATAMAX] = {
-
+static struct font_data fontdata_8x16 = {
+ { 0, 0, FONTDATAMAX, 0 }, {
/* 0 0x00 '^@' */
0x00, /* 00000000 */
0x00, /* 00000000 */
@@ -4619,8 +4619,7 @@ static const unsigned char fontdata_8x16[FONTDATAMAX] = {
0x00, /* 00000000 */
0x00, /* 00000000 */
0x00, /* 00000000 */
-
-};
+} };
const struct font_desc font_vga_8x16 = {
@@ -4628,7 +4627,7 @@ const struct font_desc font_vga_8x16 = {
.name = "VGA8x16",
.width = 8,
.height = 16,
- .data = fontdata_8x16,
+ .data = fontdata_8x16.data,
.pref = 0,
};
EXPORT_SYMBOL(font_vga_8x16);