From 6735b4632def0640dbdf4eb9f99816aca18c4f16 Mon Sep 17 00:00:00 2001 From: Peilin Ye Date: Thu, 24 Sep 2020 09:42:22 -0400 Subject: 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 . 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 Reviewed-by: Greg Kroah-Hartman Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/ef18af00c35fb3cc826048a5f70924ed6ddce95b.1600953813.git.yepeilin.cs@gmail.com --- lib/fonts/font_8x16.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) (limited to 'lib/fonts/font_8x16.c') diff --git a/lib/fonts/font_8x16.c b/lib/fonts/font_8x16.c index b7ab1f5fbdb8..37cedd36ca5e 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); -- cgit v1.2.3