IB/hfi1: Handle missing magic values in config file

Driver does not check whether proper configuration file exist in EPROM,
and treats empty partition as possible valid configuration, preventing
fallback to default firmware. Change EPROM read function to treat
missing magic number as read error.
Reviewed-by: Jakub Byczkowski <jakub.byczkowski@intel.com>
Signed-off-by: Jan Sokolowski <jan.sokolowski@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/hfi1/eprom.c

@@ -250,7 +250,6 @@ static int read_partition_platform_config(struct hfi1_devdata *dd, void **data,
 {
 	void *buffer;
 	void *p;
-	u32 length;
 	int ret;
 
 	buffer = kmalloc(P1_SIZE, GFP_KERNEL);
@@ -265,13 +264,13 @@ static int read_partition_platform_config(struct hfi1_devdata *dd, void **data,
 
 	/* scan for image magic that may trail the actual data */
 	p = strnstr(buffer, IMAGE_TRAIL_MAGIC, P1_SIZE);
-	if (p)
-		length = p - buffer;
-	else
-		length = P1_SIZE;
+	if (!p) {
+		kfree(buffer);
+		return -ENOENT;
+	}
 
 	*data = buffer;
-	*size = length;
+	*size = p - buffer;
 	return 0;
 }