font: Reject fonts with negative max_char_width or max_char_height

If max_char_width or max_char_height are negative wrong values can be propagated
by grub_font_get_max_char_width() or grub_font_get_max_char_height(). Prevent
this from happening.

Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/font/font.c b/grub-core/font/font.c
index 674043d0d186b592bf1df7e30f4c292853e1389f..24adcb35a8676b7abfc37069c7780e4bfef408b3 100644 (file)
--- a/grub-core/font/font.c
+++ b/grub-core/font/font.c
@@ -644,8 +644,8 @@ grub_font_load (const char *filename)
               font->max_char_width, font->max_char_height, font->num_chars);
 #endif
 
-  if (font->max_char_width == 0
-      || font->max_char_height == 0
+  if (font->max_char_width <= 0
+      || font->max_char_height <= 0
       || font->num_chars == 0
       || font->char_index == 0 || font->ascent == 0 || font->descent == 0)
     {