diff options
| author | Peilin Ye <yepeilin.cs@gmail.com> | 2020-09-24 09:42:22 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-10-14 10:32:56 +0200 |
| commit | f51ec3fd71284531205981858b192970ec46770e (patch) | |
| tree | 7612ccff89e6ee448aad87abc9a1bf3a50859b7f /include | |
| parent | eebe3685701bcd4b437f2ddd2142888b1fb39aeb (diff) | |
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 'include')
| -rw-r--r-- | include/linux/font.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/font.h b/include/linux/font.h index 40ed008d7dad..59faa80f586d 100644 --- a/include/linux/font.h +++ b/include/linux/font.h @@ -67,4 +67,9 @@ extern const struct font_desc *get_default_font(int xres, int yres, #define FONT_EXTRA_WORDS 4 +struct font_data { + unsigned int extra[FONT_EXTRA_WORDS]; + const unsigned char data[]; +} __packed; + #endif /* _VIDEO_FONT_H */ |