From: Peilin Ye <yepeilin.cs@xxxxxxxxx> 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@xxxxxxxxxxxxxxx Link: https://syzkaller.appspot.com/bug?id=08b8be45afea11888776f897895aef9ad1c3ecfd Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx> Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/ef18af00c35fb3cc826048a5f70924ed6ddce95b.1600953813.git.yepeilin.cs@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/font.h | 5 +++++ lib/fonts/font_10x18.c | 9 ++++----- lib/fonts/font_6x10.c | 9 +++++---- lib/fonts/font_6x11.c | 9 ++++----- lib/fonts/font_7x14.c | 9 ++++----- lib/fonts/font_8x16.c | 9 ++++----- lib/fonts/font_8x8.c | 9 ++++----- lib/fonts/font_acorn_8x8.c | 9 ++++++--- lib/fonts/font_mini_4x6.c | 8 ++++---- lib/fonts/font_pearl_8x8.c | 9 ++++----- lib/fonts/font_sun12x22.c | 9 ++++----- lib/fonts/font_sun8x16.c | 7 ++++--- 12 files changed, 52 insertions(+), 49 deletions(-) --- a/include/linux/font.h +++ b/include/linux/font.h @@ -65,4 +65,9 @@ extern const struct font_desc *get_defau #define FONT_EXTRA_WORDS 4 +struct font_data { + unsigned int extra[FONT_EXTRA_WORDS]; + const unsigned char data[]; +} __packed; + #endif /* _VIDEO_FONT_H */ --- a/lib/fonts/font_10x18.c +++ b/lib/fonts/font_10x18.c @@ -7,8 +7,8 @@ #define FONTDATAMAX 9216 -static const unsigned char fontdata_10x18[FONTDATAMAX] = { - +static struct font_data fontdata_10x18 = { + { 0, 0, FONTDATAMAX, 0 }, { /* 0 0x00 '^@' */ 0x00, 0x00, /* 0000000000 */ 0x00, 0x00, /* 0000000000 */ @@ -5128,8 +5128,7 @@ static const unsigned char fontdata_10x1 0x00, 0x00, /* 0000000000 */ 0x00, 0x00, /* 0000000000 */ 0x00, 0x00, /* 0000000000 */ - -}; +} }; const struct font_desc font_10x18 = { @@ -5137,7 +5136,7 @@ const struct font_desc font_10x18 = { .name = "10x18", .width = 10, .height = 18, - .data = fontdata_10x18, + .data = fontdata_10x18.data, #ifdef __sparc__ .pref = 5, #else --- a/lib/fonts/font_6x10.c +++ b/lib/fonts/font_6x10.c @@ -1,7 +1,9 @@ #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 */ @@ -3073,14 +3075,13 @@ 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, }; --- a/lib/fonts/font_6x11.c +++ b/lib/fonts/font_6x11.c @@ -8,8 +8,8 @@ #define FONTDATAMAX (11*256) -static const unsigned char fontdata_6x11[FONTDATAMAX] = { - +static struct font_data fontdata_6x11 = { + { 0, 0, FONTDATAMAX, 0 }, { /* 0 0x00 '^@' */ 0x00, /* 00000000 */ 0x00, /* 00000000 */ @@ -3337,8 +3337,7 @@ static const unsigned char fontdata_6x11 0x00, /* 00000000 */ 0x00, /* 00000000 */ 0x00, /* 00000000 */ - -}; +} }; const struct font_desc font_vga_6x11 = { @@ -3346,7 +3345,7 @@ const struct font_desc font_vga_6x11 = { .name = "ProFont6x11", .width = 6, .height = 11, - .data = fontdata_6x11, + .data = fontdata_6x11.data, /* Try avoiding this font if possible unless on MAC */ .pref = -2000, }; --- a/lib/fonts/font_7x14.c +++ b/lib/fonts/font_7x14.c @@ -7,8 +7,8 @@ #define FONTDATAMAX 3584 -static const unsigned char fontdata_7x14[FONTDATAMAX] = { - +static struct font_data fontdata_7x14 = { + { 0, 0, FONTDATAMAX, 0 }, { /* 0 0x00 '^@' */ 0x00, /* 0000000 */ 0x00, /* 0000000 */ @@ -4104,8 +4104,7 @@ static const unsigned char fontdata_7x14 0x00, /* 0000000 */ 0x00, /* 0000000 */ 0x00, /* 0000000 */ - -}; +} }; const struct font_desc font_7x14 = { @@ -4113,6 +4112,6 @@ const struct font_desc font_7x14 = { .name = "7x14", .width = 7, .height = 14, - .data = fontdata_7x14, + .data = fontdata_7x14.data, .pref = 0, }; --- a/lib/fonts/font_8x16.c +++ b/lib/fonts/font_8x16.c @@ -9,8 +9,8 @@ #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 */ @@ -4618,8 +4618,7 @@ static const unsigned char fontdata_8x16 0x00, /* 00000000 */ 0x00, /* 00000000 */ 0x00, /* 00000000 */ - -}; +} }; const struct font_desc font_vga_8x16 = { @@ -4627,7 +4626,7 @@ 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); --- a/lib/fonts/font_8x8.c +++ b/lib/fonts/font_8x8.c @@ -8,8 +8,8 @@ #define FONTDATAMAX 2048 -static const unsigned char fontdata_8x8[FONTDATAMAX] = { - +static struct font_data fontdata_8x8 = { + { 0, 0, FONTDATAMAX, 0 }, { /* 0 0x00 '^@' */ 0x00, /* 00000000 */ 0x00, /* 00000000 */ @@ -2569,8 +2569,7 @@ static const unsigned char fontdata_8x8[ 0x00, /* 00000000 */ 0x00, /* 00000000 */ 0x00, /* 00000000 */ - -}; +} }; const struct font_desc font_vga_8x8 = { @@ -2578,6 +2577,6 @@ const struct font_desc font_vga_8x8 = { .name = "VGA8x8", .width = 8, .height = 8, - .data = fontdata_8x8, + .data = fontdata_8x8.data, .pref = 0, }; --- a/lib/fonts/font_acorn_8x8.c +++ b/lib/fonts/font_acorn_8x8.c @@ -2,7 +2,10 @@ #include <linux/font.h> -static const unsigned char acorndata_8x8[] = { +#define FONTDATAMAX 2048 + +static struct font_data acorndata_8x8 = { +{ 0, 0, FONTDATAMAX, 0 }, { /* 00 */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* ^@ */ /* 01 */ 0x7e, 0x81, 0xa5, 0x81, 0xbd, 0x99, 0x81, 0x7e, /* ^A */ /* 02 */ 0x7e, 0xff, 0xbd, 0xff, 0xc3, 0xe7, 0xff, 0x7e, /* ^B */ @@ -259,14 +262,14 @@ static const unsigned char acorndata_8x8 /* FD */ 0x38, 0x04, 0x18, 0x20, 0x3c, 0x00, 0x00, 0x00, /* FE */ 0x00, 0x00, 0x3c, 0x3c, 0x3c, 0x3c, 0x00, 0x00, /* FF */ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 -}; +} }; const struct font_desc font_acorn_8x8 = { .idx = ACORN8x8_IDX, .name = "Acorn8x8", .width = 8, .height = 8, - .data = acorndata_8x8, + .data = acorndata_8x8.data, #ifdef CONFIG_ARCH_ACORN .pref = 20, #else --- a/lib/fonts/font_mini_4x6.c +++ b/lib/fonts/font_mini_4x6.c @@ -43,8 +43,8 @@ __END__; #define FONTDATAMAX 1536 -static const unsigned char fontdata_mini_4x6[FONTDATAMAX] = { - +static struct font_data fontdata_mini_4x6 = { + { 0, 0, FONTDATAMAX, 0 }, { /*{*/ /* Char 0: ' ' */ 0xee, /*= [*** ] */ @@ -2145,14 +2145,14 @@ static const unsigned char fontdata_mini 0xee, /*= [*** ] */ 0x00, /*= [ ] */ /*}*/ -}; +} }; const struct font_desc font_mini_4x6 = { .idx = MINI4x6_IDX, .name = "MINI4x6", .width = 4, .height = 6, - .data = fontdata_mini_4x6, + .data = fontdata_mini_4x6.data, .pref = 3, }; --- a/lib/fonts/font_pearl_8x8.c +++ b/lib/fonts/font_pearl_8x8.c @@ -13,8 +13,8 @@ #define FONTDATAMAX 2048 -static const unsigned char fontdata_pearl8x8[FONTDATAMAX] = { - +static struct font_data fontdata_pearl8x8 = { + { 0, 0, FONTDATAMAX, 0 }, { /* 0 0x00 '^@' */ 0x00, /* 00000000 */ 0x00, /* 00000000 */ @@ -2574,14 +2574,13 @@ static const unsigned char fontdata_pear 0x00, /* 00000000 */ 0x00, /* 00000000 */ 0x00, /* 00000000 */ - -}; +} }; const struct font_desc font_pearl_8x8 = { .idx = PEARL8x8_IDX, .name = "PEARL8x8", .width = 8, .height = 8, - .data = fontdata_pearl8x8, + .data = fontdata_pearl8x8.data, .pref = 2, }; --- a/lib/fonts/font_sun12x22.c +++ b/lib/fonts/font_sun12x22.c @@ -2,8 +2,8 @@ #define FONTDATAMAX 11264 -static const unsigned char fontdata_sun12x22[FONTDATAMAX] = { - +static struct font_data fontdata_sun12x22 = { + { 0, 0, FONTDATAMAX, 0 }, { /* 0 0x00 '^@' */ 0x00, 0x00, /* 000000000000 */ 0x00, 0x00, /* 000000000000 */ @@ -6147,8 +6147,7 @@ static const unsigned char fontdata_sun1 0x00, 0x00, /* 000000000000 */ 0x00, 0x00, /* 000000000000 */ 0x00, 0x00, /* 000000000000 */ - -}; +} }; const struct font_desc font_sun_12x22 = { @@ -6156,7 +6155,7 @@ const struct font_desc font_sun_12x22 = .name = "SUN12x22", .width = 12, .height = 22, - .data = fontdata_sun12x22, + .data = fontdata_sun12x22.data, #ifdef __sparc__ .pref = 5, #else --- a/lib/fonts/font_sun8x16.c +++ b/lib/fonts/font_sun8x16.c @@ -2,7 +2,8 @@ #define FONTDATAMAX 4096 -static const unsigned char fontdata_sun8x16[FONTDATAMAX] = { +static struct font_data fontdata_sun8x16 = { +{ 0, 0, FONTDATAMAX, 0 }, { /* */ 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* */ 0x00,0x00,0x7e,0x81,0xa5,0x81,0x81,0xbd,0x99,0x81,0x81,0x7e,0x00,0x00,0x00,0x00, /* */ 0x00,0x00,0x7e,0xff,0xdb,0xff,0xff,0xc3,0xe7,0xff,0xff,0x7e,0x00,0x00,0x00,0x00, @@ -259,14 +260,14 @@ static const unsigned char fontdata_sun8 /* */ 0x00,0x70,0xd8,0x30,0x60,0xc8,0xf8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, /* */ 0x00,0x00,0x00,0x00,0x7c,0x7c,0x7c,0x7c,0x7c,0x7c,0x7c,0x00,0x00,0x00,0x00,0x00, /* */ 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, -}; +} }; const struct font_desc font_sun_8x16 = { .idx = SUN8x16_IDX, .name = "SUN8x16", .width = 8, .height = 16, - .data = fontdata_sun8x16, + .data = fontdata_sun8x16.data, #ifdef __sparc__ .pref = 10, #else
