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- 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 Sørensen <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
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