ip maddr show” on an infiniband address causes a stack corruption

“ip maddr show” on an infiniband address causes a stack corruption
because the length of the address for Infiniband (20 bytes, as
described in kernel doc Documentation/infiniband/ipoib.txt) does not
fit on the 16 bytes of the field in which it gets stored.

The proposed patch increases the size of the hardware address from 4
__u32 to 8 and also adds a check to avoid overriding the available
size while parsing the hardware address.

This bug affects current upstream code AFAICT.

Hope this helps,
Cheers,
Olivier.

“ip maddr show ib0” causes a stack corruption because the length of the address
for Infiniband (20 see kernel doc Documentation/infiniband/ipoib.txt) does not
fit on the 16 bytes of the field in which it gets stored.

The proposed patch increases the size of the hardware address from 4 u32 to 8
and adds a check to avoid overriding the available size while parsing the
hardware address.

include/utils.h

@@ -46,7 +46,7 @@ typedef struct
 	__u8 bytelen;
 	__s16 bitlen;
 	__u32 flags;
-	__u32 data[4];
+	__u32 data[8];
 } inet_prefix;
 
 #define PREFIXLEN_SPECIFIED 1

ip/ipmaddr.c

@@ -43,11 +43,11 @@ static void usage(void)
 	exit(-1);
 }
 
-static int parse_hex(char *str, unsigned char *addr)
+static int parse_hex(char *str, unsigned char *addr, size_t size)
 {
 	int len=0;
 
-	while (*str) {
+	while (*str && (len < 2 * size)) {
 		int tmp;
 		if (str[1] == 0)
 			return -1;
@@ -104,7 +104,7 @@ void read_dev_mcast(struct ma_info **result_p)
 
 		m.addr.family = AF_PACKET;
 
-		len = parse_hex(hexa, (unsigned char*)&m.addr.data);
+		len = parse_hex(hexa, (unsigned char*)&m.addr.data, sizeof (m.addr.data));
 		if (len >= 0) {
 			struct ma_info *ma = malloc(sizeof(m));
 
@@ -176,7 +176,7 @@ void read_igmp6(struct ma_info **result_p)
 
 		m.addr.family = AF_INET6;
 
-		len = parse_hex(hexa, (unsigned char*)&m.addr.data);
+		len = parse_hex(hexa, (unsigned char*)&m.addr.data, sizeof (m.addr.data));
 		if (len >= 0) {
 			struct ma_info *ma = malloc(sizeof(m));