tablet/grub
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

font: Fix integer overflow in BMP index

Browse Source 
The BMP index (font->bmp_idx) is designed as a reverse lookup table of
char entries (font->char_index), in order to speed up lookups for BMP
chars (i.e. code < 0x10000). The values in BMP index are the subscripts
of the corresponding char entries, stored in grub_uint16_t, while 0xffff
means not found.

This patch fixes the problem of large subscript truncated to grub_uint16_t,
leading BMP index to return wrong char entry or report false miss. The
code now checks for bounds and uses BMP index as a hint, and fallbacks
to binary-search if necessary.

On the occasion add a comment about BMP index is initialized to 0xffff.

Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Zhang Boyang 2022-08-15 02:04:58 +08:00 committed by Daniel Kiper
parent 23843fe894
commit b9396daf1c
1 changed files with 9 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
grub-core/font/font.c
View File

@ -300,6 +300,8 @@ load_font_index (grub_file_t file, grub_uint32_t sect_length, struct
font->bmp_idx = grub_malloc (0x10000 * sizeof (grub_uint16_t));
if (!font->bmp_idx)
return 1;
/* Init the BMP index array to 0xffff. */
grub_memset (font->bmp_idx, 0xff, 0x10000 * sizeof (grub_uint16_t));
@ -328,7 +330,7 @@ load_font_index (grub_file_t file, grub_uint32_t sect_length, struct
return 1;
}
if (entry->code < 0x10000)
if (entry->code < 0x10000 && i < 0xffff)
font->bmp_idx[entry->code] = i;
last_code = entry->code;
@ -696,9 +698,12 @@ find_glyph (const grub_font_t font, grub_uint32_t code)
/* Use BMP index if possible. */
if (code < 0x10000 && font->bmp_idx)
{
if (font->bmp_idx[code] == 0xffff)
return 0;
return &table[font->bmp_idx[code]];
if (font->bmp_idx[code] < 0xffff)
return &table[font->bmp_idx[code]];
/*
* When we are here then lookup in BMP index result in miss,
* fallthough to binary-search.
*/
}
/* Do a binary search in `char_index', which is ordered by code point. */