[PATCH] virFileResolveLink: fix return value

[Eric Blake <eblake@xxxxxxxxxx>]

virFileResolveLink was returning a positive value on error,
thus confusing callers that assumed failure was < 0.  The
confusion is further evidenced by callers that would have
ended up calling virReportSystemError with a negative value
instead of a valid errno.

Fixes Red Hat BZ #591363.

* src/util/util.c (virFileResolveLink): Live up to documentation.
* src/qemu/qemu_security_dac.c
(qemuSecurityDACRestoreSecurityFileLabel): Adjust callers.
* src/security/security_selinux.c
(SELinuxRestoreSecurityFileLabel): Likewise.
* src/storage/storage_backend_disk.c
(virStorageBackendDiskDeleteVol): Likewise.
---

Thanks to Daniel P. Berrange for helping isolate the cause
of the bugzilla failure.  I validated that the only instance
of 'cannot stat %s' in libvirt.po comes from
SELinuxRestoreSecurityFileLabel, and that it does indeed
have the ability to dereference a NULL pointer before this fix.

 src/qemu/qemu_security_dac.c       |    5 ++---
 src/security/security_selinux.c    |    7 +++----
 src/storage/storage_backend_disk.c |    7 +++----
 src/util/util.c                    |    6 +++---
 4 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/src/qemu/qemu_security_dac.c b/src/qemu/qemu_security_dac.c
index 364227d..a816441 100644
--- a/src/qemu/qemu_security_dac.c
+++ b/src/qemu/qemu_security_dac.c
@@ -75,13 +75,12 @@ qemuSecurityDACRestoreSecurityFileLabel(const char *path)
 {
     struct stat buf;
     int rc = -1;
-    int err;
     char *newpath = NULL;

     VIR_INFO("Restoring DAC user and group on '%s'", path);

-    if ((err = virFileResolveLink(path, &newpath)) < 0) {
-        virReportSystemError(err,
+    if (virFileResolveLink(path, &newpath) < 0) {
+        virReportSystemError(errno,
                              _("cannot resolve symlink %s"), path);
         goto err;
     }
diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c
index 47534df..669ef42 100644
--- a/src/security/security_selinux.c
+++ b/src/security/security_selinux.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008,2009 Red Hat, Inc.
+ * Copyright (C) 2008-2010 Red Hat, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -353,13 +353,12 @@ SELinuxRestoreSecurityFileLabel(const char *path)
     struct stat buf;
     security_context_t fcon = NULL;
     int rc = -1;
-    int err;
     char *newpath = NULL;

     VIR_INFO("Restoring SELinux context on '%s'", path);

-    if ((err = virFileResolveLink(path, &newpath)) < 0) {
-        virReportSystemError(err,
+    if (virFileResolveLink(path, &newpath) < 0) {
+        virReportSystemError(errno,
                              _("cannot resolve symlink %s"), path);
         goto err;
     }
diff --git a/src/storage/storage_backend_disk.c b/src/storage/storage_backend_disk.c
index 836d1ca..7188386 100644
--- a/src/storage/storage_backend_disk.c
+++ b/src/storage/storage_backend_disk.c
@@ -1,7 +1,7 @@
 /*
  * storage_backend_disk.c: storage backend for disk handling
  *
- * Copyright (C) 2007-2008 Red Hat, Inc.
+ * Copyright (C) 2007-2008, 2010 Red Hat, Inc.
  * Copyright (C) 2007-2008 Daniel P. Berrange
  *
  * This library is free software; you can redistribute it and/or
@@ -612,13 +612,12 @@ virStorageBackendDiskDeleteVol(virConnectPtr conn ATTRIBUTE_UNUSED,
                                unsigned int flags ATTRIBUTE_UNUSED)
 {
     char *part_num = NULL;
-    int err;
     char *devpath = NULL;
     char *devname, *srcname;
     int rc = -1;

-    if ((err = virFileResolveLink(vol->target.path, &devpath)) < 0) {
-        virReportSystemError(err,
+    if (virFileResolveLink(vol->target.path, &devpath) < 0) {
+        virReportSystemError(errno,
                              _("Couldn't read volume target path '%s'"),
                              vol->target.path);
         goto cleanup;
diff --git a/src/util/util.c b/src/util/util.c
index 26ac6ba..e937d39 100644
--- a/src/util/util.c
+++ b/src/util/util.c
@@ -1182,7 +1182,7 @@ int virFileLinkPointsTo(const char *checkLink,
  * real path
  *
  * Return 0 if path was not a symbolic, or the link was
- * resolved. Return -1 upon error
+ * resolved. Return -1 with errno set upon error
  */
 int virFileResolveLink(const char *linkpath,
                        char **resultpath)
@@ -1192,11 +1192,11 @@ int virFileResolveLink(const char *linkpath,
     *resultpath = NULL;

     if (lstat(linkpath, &st) < 0)
-        return errno;
+        return -1;

     if (!S_ISLNK(st.st_mode)) {
         if (!(*resultpath = strdup(linkpath)))
-            return -ENOMEM;
+            return -1;
         return 0;
     }

-- 
1.7.0.1

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