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

font: Fix integer underflow in binary search of char index

Browse Source 
If search target is less than all entries in font->index then "hi"
variable is set to -1, which translates to SIZE_MAX and leads to errors.

This patch fixes the problem by replacing the entire binary search code
with the libstdc++'s std::lower_bound() implementation.

Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Zhang Boyang 2022-08-14 18:09:38 +08:00 committed by Daniel Kiper
parent b9396daf1c
commit 1d2015598c
1 changed files with 22 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
grub-core/font/font.c
View File

@ -688,12 +688,12 @@ read_be_int16 (grub_file_t file, grub_int16_t * value)
static inline struct char_index_entry *
find_glyph (const grub_font_t font, grub_uint32_t code)
{
struct char_index_entry *table;
grub_size_t lo;
grub_size_t hi;
grub_size_t mid;
struct char_index_entry *table, *first, *end;
grub_size_t len;
table = font->char_index;
if (table == NULL)
return NULL;
/* Use BMP index if possible. */
if (code < 0x10000 && font->bmp_idx)
@ -706,25 +706,29 @@ find_glyph (const grub_font_t font, grub_uint32_t code)
*/
}
/* Do a binary search in `char_index', which is ordered by code point. */
lo = 0;
hi = font->num_chars - 1;
/*
* Do a binary search in char_index which is ordered by code point.
* The code below is the same as libstdc++'s std::lower_bound().
*/
first = table;
len = font->num_chars;
end = first + len;
if (!table)
return 0;
while (lo <= hi)
while (len > 0)
{
mid = lo + (hi - lo) / 2;
if (code < table[mid].code)
hi = mid - 1;
else if (code > table[mid].code)
lo = mid + 1;
grub_size_t half = len >> 1;
struct char_index_entry *middle = first + half;
if (middle->code < code)
{
first = middle + 1;
len = len - half - 1;
}
else
return &table[mid];
len = half;
}
return 0;
return (first < end && first->code == code) ? first : NULL;
}
/* Get a glyph for the Unicode character CODE in FONT. The glyph is loaded