Blame SOURCES/0567-font-Fix-integer-overflow-in-BMP-index.patch

530103
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
530103
From: Zhang Boyang <zhangboyang.id@gmail.com>
530103
Date: Mon, 15 Aug 2022 02:04:58 +0800
530103
Subject: [PATCH] font: Fix integer overflow in BMP index
530103
530103
The BMP index (font->bmp_idx) is designed as a reverse lookup table of
530103
char entries (font->char_index), in order to speed up lookups for BMP
530103
chars (i.e. code < 0x10000). The values in BMP index are the subscripts
530103
of the corresponding char entries, stored in grub_uint16_t, while 0xffff
530103
means not found.
530103
530103
This patch fixes the problem of large subscript truncated to grub_uint16_t,
530103
leading BMP index to return wrong char entry or report false miss. The
530103
code now checks for bounds and uses BMP index as a hint, and fallbacks
530103
to binary-search if necessary.
530103
530103
On the occasion add a comment about BMP index is initialized to 0xffff.
530103
530103
Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
530103
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
530103
(cherry picked from commit afda8b60ba0712abe01ae1e64c5f7a067a0e6492)
530103
(cherry picked from commit 6d90568929e11739b56f09ebbce9185ca9c23519)
530103
(cherry picked from commit b8c47c3dd6894b3135db861e3e563f661efad5c3)
530103
---
530103
 grub-core/font/font.c | 13 +++++++++----
530103
 1 file changed, 9 insertions(+), 4 deletions(-)
530103
530103
diff --git a/grub-core/font/font.c b/grub-core/font/font.c
530103
index 1367e44743..059c23dff7 100644
530103
--- a/grub-core/font/font.c
530103
+++ b/grub-core/font/font.c
530103
@@ -300,6 +300,8 @@ load_font_index (grub_file_t file, grub_uint32_t sect_length, struct
530103
   font->bmp_idx = grub_malloc (0x10000 * sizeof (grub_uint16_t));
530103
   if (!font->bmp_idx)
530103
     return 1;
530103
+
530103
+  /* Init the BMP index array to 0xffff. */
530103
   grub_memset (font->bmp_idx, 0xff, 0x10000 * sizeof (grub_uint16_t));
530103
 
530103
 
530103
@@ -328,7 +330,7 @@ load_font_index (grub_file_t file, grub_uint32_t sect_length, struct
530103
 	  return 1;
530103
 	}
530103
 
530103
-      if (entry->code < 0x10000)
530103
+      if (entry->code < 0x10000 && i < 0xffff)
530103
 	font->bmp_idx[entry->code] = i;
530103
 
530103
       last_code = entry->code;
530103
@@ -696,9 +698,12 @@ find_glyph (const grub_font_t font, grub_uint32_t code)
530103
   /* Use BMP index if possible.  */
530103
   if (code < 0x10000 && font->bmp_idx)
530103
     {
530103
-      if (font->bmp_idx[code] == 0xffff)
530103
-	return 0;
530103
-      return &table[font->bmp_idx[code]];
530103
+      if (font->bmp_idx[code] < 0xffff)
530103
+	return &table[font->bmp_idx[code]];
530103
+      /*
530103
+       * When we are here then lookup in BMP index result in miss,
530103
+       * fallthough to binary-search.
530103
+       */
530103
     }
530103
 
530103
   /* Do a binary search in `char_index', which is ordered by code point.  */