[TG3]: Fix array overrun in tg3_read_partno().

Use proper upper limits for the loops and check for all error
conditions.

The problem was noticed by Adrian Bunk.

Signed-off-by: Michael Chan <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/tg3.c

···
 static void __devinit tg3_read_partno(struct tg3 *tp)
 {
 	unsigned char vpd_data[256];
-	int i;
+	unsigned int i;
 	u32 magic;
 
 	if (tg3_nvram_read_swab(tp, 0x0, &magic))
···
 	}
 
 	/* Now parse and find the part number. */
-	for (i = 0; i < 256; ) {
+	for (i = 0; i < 254; ) {
 		unsigned char val = vpd_data[i];
-		int block_end;
+		unsigned int block_end;
 
 		if (val == 0x82 || val == 0x91) {
 			i = (i + 3 +
···
 			     (vpd_data[i + 1] +
 			      (vpd_data[i + 2] << 8)));
 		i += 3;
-		while (i < block_end) {
+
+		if (block_end > 256)
+			goto out_not_found;
+
+		while (i < (block_end - 2)) {
 			if (vpd_data[i + 0] == 'P' &&
 			    vpd_data[i + 1] == 'N') {
 				int partno_len = vpd_data[i + 2];
 
-				if (partno_len > 24)
+				i += 3;
+				if (partno_len > 24 || (partno_len + i) > 256)
 					goto out_not_found;
 
 				memcpy(tp->board_part_number,
-				       &vpd_data[i + 3],
-				       partno_len);
+				       &vpd_data[i], partno_len);
 
 				/* Success. */
 				return;
 			}
+			i += 3 + vpd_data[i + 2];
 		}
 
 		/* Part number not found. */