[PATCH] nss: Skip empty files and avoid use of uninitialized value

[Jiang XueQian <jiangxueqian@xxxxxxxxx>]

JSON parser isn't called when reading empty files so `jerr` will be used
uninitialized in the original code. Empty files appear when a network
has no dhcp clients.

This patch checks for such files and skip them.

Signed-off-by: Jiang XueQian <jiangxueqian@xxxxxxxxx>
---
 tools/nss/libvirt_nss_leases.c | 5 +++++
 tools/nss/libvirt_nss_macs.c   | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/tools/nss/libvirt_nss_leases.c b/tools/nss/libvirt_nss_leases.c
index aea81bb56e..7ffe4a8761 100644
--- a/tools/nss/libvirt_nss_leases.c
+++ b/tools/nss/libvirt_nss_leases.c
@@ -290,6 +290,11 @@ findLeases(const char *file,
         jerr = json_tokener_get_error(tok);
     } while (jerr == json_tokener_continue);
 
+    if (nreadTotal == 0) {
+        ret = 0;
+        goto cleanup;
+    }
+
     if (jerr == json_tokener_continue) {
         ERROR("Cannot parse %s: incomplete json found", file);
         goto cleanup;
diff --git a/tools/nss/libvirt_nss_macs.c b/tools/nss/libvirt_nss_macs.c
index 23229a18f3..57c0f79fbb 100644
--- a/tools/nss/libvirt_nss_macs.c
+++ b/tools/nss/libvirt_nss_macs.c
@@ -152,6 +152,11 @@ findMACs(const char *file,
         jerr = json_tokener_get_error(tok);
     } while (jerr == json_tokener_continue);
 
+    if (nreadTotal == 0) {
+        ret = 0;
+        goto cleanup;
+    }
+
     if (jerr == json_tokener_continue) {
         ERROR("Cannot parse %s: incomplete json found", file);
         goto cleanup;
-- 
2.48.1