[PATCH 1/2] inetmib: Avoid overflows in IPv4 address comparisons.

[Francois Gouget]

The difference between two ULONGs may not fit in an int, causing
comparison errors.

Signed-off-by: Francois Gouget <fgouget at codeweavers.com>
---
compareIpAddrRow() and oidToIpForwardRow() should also do byte-swapping
which will be done in the next patch.
---
 dlls/inetmib1/main.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/dlls/inetmib1/main.c b/dlls/inetmib1/main.c
index 90da277375e..d19648ff792 100644
--- a/dlls/inetmib1/main.c
+++ b/dlls/inetmib1/main.c
@@ -772,9 +772,11 @@ static void oidToIpAddrRow(AsnObjectIdentifier *oid, void *dst)
 
 static int __cdecl compareIpAddrRow(const void *a, const void *b)
 {
-    const MIB_IPADDRROW *key = a, *value = b;
+    const MIB_IPADDRROW *rowA = a, *rowB = b;
 
-    return key->dwAddr - value->dwAddr;
+    return rowA->dwAddr < rowB->dwAddr ? -1 : /* avoids overflows */
+           rowA->dwAddr > rowB->dwAddr ? 1 :
+           0;
 }
 
 static BOOL mib2IpAddrQuery(BYTE bPduType, SnmpVarBind *pVarBind,
@@ -865,9 +867,11 @@ static void oidToIpForwardRow(AsnObjectIdentifier *oid, void *dst)
 
 static int __cdecl compareIpForwardRow(const void *a, const void *b)
 {
-    const MIB_IPFORWARDROW *key = a, *value = b;
+    const MIB_IPFORWARDROW *rowA = a, *rowB = b;
 
-    return key->dwForwardDest - value->dwForwardDest;
+    return rowA->dwForwardDest < rowB->dwForwardDest ? -1 : /* avoids overflows */
+           rowA->dwForwardDest > rowB->dwForwardDest ? 1 :
+           0;
 }
 
 static BOOL mib2IpRouteQuery(BYTE bPduType, SnmpVarBind *pVarBind,
@@ -1223,13 +1227,13 @@ static void oidToUdpRow(AsnObjectIdentifier *oid, void *dst)
 
 static int __cdecl compareUdpRow(const void *a, const void *b)
 {
-    const MIB_UDPROW *key = a, *value = b;
-    int ret;
+    const MIB_UDPROW *rowA = a, *rowB = b;
+    ULONG addrA = ntohl( rowA->dwLocalAddr );
+    ULONG addrB = ntohl( rowB->dwLocalAddr );
 
-    ret = ntohl(key->dwLocalAddr) - ntohl(value->dwLocalAddr);
-    if (ret == 0)
-        ret = ntohs(key->dwLocalPort) - ntohs(value->dwLocalPort);
-    return ret;
+    return addrA < addrB ? -1 : /* avoids overflows */
+           addrA > addrB ? 1 :
+           ntohs(rowA->dwLocalPort) - ntohs(rowB->dwLocalPort);
 }
 
 static BOOL mib2UdpEntryQuery(BYTE bPduType, SnmpVarBind *pVarBind,
-- 
2.30.2