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Re: [PATCH] hfsplus: Prevent overflows in comparisons
From: |
Dave Vasilevsky |
Subject: |
Re: [PATCH] hfsplus: Prevent overflows in comparisons |
Date: |
Thu, 30 Dec 2010 02:46:07 -0500 |
Now with a ChangeLog entry. -V
=== modified file 'ChangeLog'
--- ChangeLog 2010-12-27 06:19:51 +0000
+++ ChangeLog 2010-12-30 07:39:45 +0000
@@ -1,3 +1,11 @@
+2010-12-30 Dave Vasilevsky <address@hidden>
+
+ * grub-core/fs/hfsplus.c: Parent field of
+ grub_hfsplus_catkey_internal should be unsigned.
+ (grub_hfsplus_cmp_catkey): Don't compare using subtraction, it
+ overflows.
+ (grub_hfsplus_cmp_extkey): Likewise
+
2010-12-27 Vladimir Serbinenko <address@hidden>
* grub-core/loader/xnu.c (grub_cmd_xnu_kernel) [! GRUB_MACHINE_EFI]:
=== modified file 'grub-core/fs/hfsplus.c'
--- grub-core/fs/hfsplus.c 2010-01-20 08:12:47 +0000
+++ grub-core/fs/hfsplus.c 2010-12-30 06:10:23 +0000
@@ -178,7 +178,7 @@
/* Internal representation of a catalog key. */
struct grub_hfsplus_catkey_internal
{
- int parent;
+ grub_uint32_t parent;
char *name;
};
@@ -520,9 +520,12 @@
int i;
int diff;
- diff = grub_be_to_cpu32 (catkey_a->parent) - catkey_b->parent;
- if (diff)
- return diff;
+ /* Safe unsigned comparison */
+ grub_uint32_t aparent = grub_be_to_cpu32 (catkey_a->parent);
+ if (aparent > catkey_b->parent)
+ return 1;
+ if (aparent < catkey_b->parent)
+ return -1;
/* Change the filename in keya so the endianness is correct. */
for (i = 0; i < grub_be_to_cpu16 (catkey_a->namelen); i++)
@@ -555,15 +558,21 @@
{
struct grub_hfsplus_extkey *extkey_a = &keya->extkey;
struct grub_hfsplus_extkey_internal *extkey_b = &keyb->extkey;
- int diff;
-
- diff = grub_be_to_cpu32 (extkey_a->fileid) - extkey_b->fileid;
-
- if (diff)
- return diff;
-
- diff = grub_be_to_cpu32 (extkey_a->start) - extkey_b->start;
- return diff;
+ grub_uint32_t akey;
+
+ /* Safe unsigned comparison */
+ akey = grub_be_to_cpu32 (extkey_a->fileid);
+ if (akey > extkey_b->fileid)
+ return 1;
+ if (akey < extkey_b->fileid)
+ return -1;
+
+ akey = grub_be_to_cpu32 (extkey_a->start);
+ if (akey > extkey_b->start)
+ return 1;
+ if (akey < extkey_b->start)
+ return -1;
+ return 0;
}
static char *