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| author | Peilin Ye <yepeilin.cs@gmail.com> | 2020-09-24 16:42:22 +0300 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2020-09-25 11:28:51 +0300 |
| commit | 6735b4632def0640dbdf4eb9f99816aca18c4f16 (patch) | |
| tree | 825c601e20be625422c729dbd83442034c1e25a0 /lib/fonts/font_6x10.c | |
| parent | bb0890b4cd7f8203e3aa99c6d0f062d6acdaad27 (diff) | |
| download | linux-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.c | 9 |
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, }; |