0102-term-gfxterm-Don-t-set-up-a-font-with-glyphs-that-ar.patch 2.2 KB

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  1. From 829329bddb2c3e623270cc634cc9ab32e6455fe7 Mon Sep 17 00:00:00 2001
  2. From: Daniel Axtens <dja@axtens.net>
  3. Date: Fri, 15 Jan 2021 20:03:20 +1100
  4. Subject: [PATCH] term/gfxterm: Don't set up a font with glyphs that are too
  5. big
  6. Catch the case where we have a font so big that it causes the number of
  7. rows or columns to be 0. Currently we continue and allocate a
  8. virtual_screen.text_buffer of size 0. We then try to use that for glpyhs
  9. and things go badly.
  10. On the emu platform, malloc() may give us a valid pointer, in which case
  11. we'll access heap memory which we shouldn't. Alternatively, it may give us
  12. NULL, in which case we'll crash. For other platforms, if I understand
  13. grub_memalign() correctly, we will receive a valid but small allocation
  14. that we will very likely later overrun.
  15. Prevent the creation of a virtual screen that isn't at least 40 cols
  16. by 12 rows. This is arbitrary, but it seems that if your width or height
  17. is half a standard 80x24 terminal, you're probably going to struggle to
  18. read anything anyway.
  19. Signed-off-by: Daniel Axtens <dja@axtens.net>
  20. Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
  21. Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
  22. ---
  23. grub-core/term/gfxterm.c | 9 +++++++++
  24. 1 file changed, 9 insertions(+)
  25. diff --git a/grub-core/term/gfxterm.c b/grub-core/term/gfxterm.c
  26. index af7c090..b40fcce 100644
  27. --- a/grub-core/term/gfxterm.c
  28. +++ b/grub-core/term/gfxterm.c
  29. @@ -232,6 +232,15 @@ grub_virtual_screen_setup (unsigned int x, unsigned int y,
  30. virtual_screen.columns = virtual_screen.width / virtual_screen.normal_char_width;
  31. virtual_screen.rows = virtual_screen.height / virtual_screen.normal_char_height;
  32. + /*
  33. + * There must be a minimum number of rows and columns for the screen to
  34. + * make sense. Arbitrarily pick half of 80x24. If either dimensions is 0
  35. + * we would allocate 0 bytes for the text_buffer.
  36. + */
  37. + if (virtual_screen.columns < 40 || virtual_screen.rows < 12)
  38. + return grub_error (GRUB_ERR_BAD_FONT,
  39. + "font: glyphs too large to fit on screen");
  40. +
  41. /* Allocate memory for text buffer. */
  42. virtual_screen.text_buffer =
  43. (struct grub_colored_char *) grub_malloc (virtual_screen.columns
  44. --
  45. 2.14.2