util: fix two virCompareLimitUlong bugs

The helper function virCompareLimitUlong compares limit values,
where value of 0 is equal to unlimited. If the latter parameter is 0,
it should return -1 instead of 1, hence the user can only set hard_limit when
swap_hard_limit currently is unlimited.

Worse, all callers pass 2 64-bit values, but on 32-bit platforms,
the second argument was silently truncated to 32 bits, which
could lead to incorrect computations.
Signed-off-by: NBing Bu Cao <mars@linux.vnet.ibm.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

src/util/virutil.c

@@ -2062,11 +2062,14 @@ virFindFCHostCapableVport(const char *sysfs_prefix ATTRIBUTE_UNUSED)
  * Returns 0 if the numbers are equal, -1 if b is greater, 1 if a is greater.
  */
 int
-virCompareLimitUlong(unsigned long long a, unsigned long b)
+virCompareLimitUlong(unsigned long long a, unsigned long long b)
 {
     if (a == b)
         return 0;
 
+    if (!b)
+        return -1;
+
     if (a == 0 || a > b)
         return 1;
 

src/util/virutil.h

@@ -168,7 +168,7 @@ char *virGetFCHostNameByWWN(const char *sysfs_prefix,
 
 char *virFindFCHostCapableVport(const char *sysfs_prefix);
 
-int virCompareLimitUlong(unsigned long long a, unsigned long b);
+int virCompareLimitUlong(unsigned long long a, unsigned long long b);
 
 int virParseOwnershipIds(const char *label, uid_t *uidPtr, gid_t *gidPtr);