[libvirt] [PATCH 3/6] Fix error handling of readdir() in virFileLoopDeviceOpen

[Daniel P. Berrange]

From: "Daniel P. Berrange" <berrange at redhat.com>

To correctly handle errors from readdir() you must set 'errno'
to zero before invoking it & check its value afterwards to
distinguish error from EOF.

Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
---
 src/util/virfile.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/util/virfile.c b/src/util/virfile.c
index 25a0501..9363468 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -531,6 +531,7 @@ static int virFileLoopDeviceOpen(char **dev_name)
         goto cleanup;
     }
 
+    errno = 0;
     while ((de = readdir(dh)) != NULL) {
         if (!STRPREFIX(de->d_name, "loop"))
             continue;
@@ -562,10 +563,15 @@ static int virFileLoopDeviceOpen(char **dev_name)
         /* Oh well, try the next device */
         VIR_FORCE_CLOSE(fd);
         VIR_FREE(looppath);
+        errno = 0;
     }
 
-    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
-                   _("Unable to find a free loop device in /dev"));
+    if (errno != 0)
+        virReportSystemError(errno, "%s",
+                             _("Unable to iterate over loop devices"));
+    else
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Unable to find a free loop device in /dev"));
 
 cleanup:
     if (fd != -1) {
-- 
1.8.2.1