security_dac: Restore label on failed chown() attempt

It's important to keep XATTRs untouched (well, in the same state
they were in when entering the function). Otherwise our
refcounting would be messed up.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/security/security_dac.c

@@ -718,7 +718,25 @@ virSecurityDACSetOwnership(virSecurityManagerPtr mgr,
     VIR_INFO("Setting DAC user and group on '%s' to '%ld:%ld'",
              NULLSTR(src ? src->path : path), (long)uid, (long)gid);
 
-    return virSecurityDACSetOwnershipInternal(priv, src, path, uid, gid);
+    if (virSecurityDACSetOwnershipInternal(priv, src, path, uid, gid) < 0) {
+        virErrorPtr origerr;
+
+        virErrorPreserveLast(&origerr);
+        /* Try to restore the label. This is done so that XATTRs
+         * are left in the same state as when the control entered
+         * this function. However, if our attempt fails, there's
+         * not much we can do. XATTRs refcounting is fubar'ed and
+         * the only option we have is warn users. */
+        if (virSecurityDACRestoreFileLabelInternal(mgr, src, path) < 0)
+            VIR_WARN("Unable to restore label on '%s'. "
+                     "XATTRs might have been left in inconsistent state.",
+                     NULLSTR(src ? src->path : path));
+
+        virErrorRestore(&origerr);
+        return -1;
+    }
+
+    return 0;
 }