ncr5380: Fix off-by-one bug in extended_msg[] bounds check

Fix the array bounds check when transferring an extended message from the
target.
Signed-off-by: NFinn Thain <fthain@telegraphics.com.au>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NOndrej Zary <linux@rainbow-software.org>
Tested-by: NMichael Schmitz <schmitzmic@gmail.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/NCR5380.c

@@ -2039,7 +2039,8 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) {
 
 					dprintk(NDEBUG_EXTENDED, "scsi%d : length=%d, code=0x%02x\n", instance->host_no, (int) extended_msg[1], (int) extended_msg[2]);
 
-					if (!len && extended_msg[1] <= (sizeof(extended_msg) - 1)) {
+					if (!len && extended_msg[1] > 0 &&
+					    extended_msg[1] <= sizeof(extended_msg) - 2) {
 						/* Accept third byte by clearing ACK */
 						NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
 						len = extended_msg[1] - 1;

drivers/scsi/atari_NCR5380.c

@@ -2330,8 +2330,8 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance)
 					dprintk(NDEBUG_EXTENDED, "scsi%d: length=%d, code=0x%02x\n", HOSTNO,
 						   (int)extended_msg[1], (int)extended_msg[2]);
 
-					if (!len && extended_msg[1] <=
-					    (sizeof(extended_msg) - 1)) {
+					if (!len && extended_msg[1] > 0 &&
+					    extended_msg[1] <= sizeof(extended_msg) - 2) {
 						/* Accept third byte by clearing ACK */
 						NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
 						len = extended_msg[1] - 1;