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authorPeilin Ye <yepeilin.cs@gmail.com>2020-09-24 16:42:22 +0300
committerDaniel Vetter <daniel.vetter@ffwll.ch>2020-09-25 11:28:51 +0300
commit6735b4632def0640dbdf4eb9f99816aca18c4f16 (patch)
tree825c601e20be625422c729dbd83442034c1e25a0 /lib/fonts/font_6x10.c
parentbb0890b4cd7f8203e3aa99c6d0f062d6acdaad27 (diff)
downloadlinux-6735b4632def0640dbdf4eb9f99816aca18c4f16.tar.xz
Fonts: Support FONT_EXTRA_WORDS macros for built-in fonts
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
Diffstat (limited to 'lib/fonts/font_6x10.c')
-rw-r--r--lib/fonts/font_6x10.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/lib/fonts/font_6x10.c b/lib/fonts/font_6x10.c
index 09b2cc03435b..87da8acd07db 100644
--- a/lib/fonts/font_6x10.c
+++ b/lib/fonts/font_6x10.c
@@ -1,8 +1,10 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/font.h>
-static const unsigned char fontdata_6x10[] = {
+#define FONTDATAMAX 2560
+static struct font_data fontdata_6x10 = {
+ { 0, 0, FONTDATAMAX, 0 }, {
/* 0 0x00 '^@' */
0x00, /* 00000000 */
0x00, /* 00000000 */
@@ -3074,14 +3076,13 @@ static const unsigned char fontdata_6x10[] = {
0x00, /* 00000000 */
0x00, /* 00000000 */
0x00, /* 00000000 */
-
-};
+} };
const struct font_desc font_6x10 = {
.idx = FONT6x10_IDX,
.name = "6x10",
.width = 6,
.height = 10,
- .data = fontdata_6x10,
+ .data = fontdata_6x10.data,
.pref = 0,
};