| From 829329bddb2c3e623270cc634cc9ab32e6455fe7 Mon Sep 17 00:00:00 2001 |
| From: Daniel Axtens <dja@axtens.net> |
| Date: Fri, 15 Jan 2021 20:03:20 +1100 |
| Subject: [PATCH] term/gfxterm: Don't set up a font with glyphs that are too |
| big |
| |
| Catch the case where we have a font so big that it causes the number of |
| rows or columns to be 0. Currently we continue and allocate a |
| virtual_screen.text_buffer of size 0. We then try to use that for glpyhs |
| and things go badly. |
| |
| On the emu platform, malloc() may give us a valid pointer, in which case |
| we'll access heap memory which we shouldn't. Alternatively, it may give us |
| NULL, in which case we'll crash. For other platforms, if I understand |
| grub_memalign() correctly, we will receive a valid but small allocation |
| that we will very likely later overrun. |
| |
| Prevent the creation of a virtual screen that isn't at least 40 cols |
| by 12 rows. This is arbitrary, but it seems that if your width or height |
| is half a standard 80x24 terminal, you're probably going to struggle to |
| read anything anyway. |
| |
| Signed-off-by: Daniel Axtens <dja@axtens.net> |
| Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> |
| Signed-off-by: Stefan SΓΈrensen <stefan.sorensen@spectralink.com> |
| --- |
| grub-core/term/gfxterm.c | 9 +++++++++ |
| 1 file changed, 9 insertions(+) |
| |
| diff --git a/grub-core/term/gfxterm.c b/grub-core/term/gfxterm.c |
| index af7c090..b40fcce 100644 |
| --- a/grub-core/term/gfxterm.c |
| +++ b/grub-core/term/gfxterm.c |
| @@ -232,6 +232,15 @@ grub_virtual_screen_setup (unsigned int x, unsigned int y, |
| virtual_screen.columns = virtual_screen.width / virtual_screen.normal_char_width; |
| virtual_screen.rows = virtual_screen.height / virtual_screen.normal_char_height; |
| |
| + /* |
| + * There must be a minimum number of rows and columns for the screen to |
| + * make sense. Arbitrarily pick half of 80x24. If either dimensions is 0 |
| + * we would allocate 0 bytes for the text_buffer. |
| + */ |
| + if (virtual_screen.columns < 40 || virtual_screen.rows < 12) |
| + return grub_error (GRUB_ERR_BAD_FONT, |
| + "font: glyphs too large to fit on screen"); |
| + |
| /* Allocate memory for text buffer. */ |
| virtual_screen.text_buffer = |
| (struct grub_colored_char *) grub_malloc (virtual_screen.columns |
| -- |
| 2.14.2 |
| |