tools/hv: Check for read/write errors

hv_kvp_daemon currently does not check whether fread() or fwrite()
succeed.  Add the necessary checks.  Also, remove the incorrect use of
feof() before fread().

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/hv/hv_kvp_daemon.c

@@ -160,7 +160,12 @@ static void kvp_update_file(int pool)
 				sizeof(struct kvp_record),
 				kvp_file_info[pool].num_records, filep);
 
-	fclose(filep);
+	if (ferror(filep) || fclose(filep)) {
+		kvp_release_lock(pool);
+		syslog(LOG_ERR, "Failed to write file, pool: %d", pool);
+		exit(EXIT_FAILURE);
+	}
+
 	kvp_release_lock(pool);
 }
 
@@ -181,12 +186,17 @@ static void kvp_update_mem_state(int pool)
 		syslog(LOG_ERR, "Failed to open file, pool: %d", pool);
 		exit(EXIT_FAILURE);
 	}
-	while (!feof(filep)) {
+	for (;;) {
 		readp = &record[records_read];
 		records_read += fread(readp, sizeof(struct kvp_record),
 					ENTRIES_PER_BLOCK * num_blocks,
 					filep);
 
+		if (ferror(filep)) {
+			syslog(LOG_ERR, "Failed to read file, pool: %d", pool);
+			exit(EXIT_FAILURE);
+		}
+
 		if (!feof(filep)) {
 			/*
 			 * We have more data to read.
@@ -249,12 +259,18 @@ static int kvp_file_init(void)
 			fclose(filep);
 			return 1;
 		}
-		while (!feof(filep)) {
+		for (;;) {
 			readp = &record[records_read];
 			records_read += fread(readp, sizeof(struct kvp_record),
 					ENTRIES_PER_BLOCK,
 					filep);
 
+			if (ferror(filep)) {
+				syslog(LOG_ERR, "Failed to read file, pool: %d",
+				       i);
+				exit(EXIT_FAILURE);
+			}
+
 			if (!feof(filep)) {
 				/*
 				 * We have more data to read.