[Xen-devel] [PATCH v2 3/3] libxl: reduce code duplication in libxl_device_vtpm_list

[Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Use recently introduced helper libxl__get_backend_from_xs_fe to handle
backend path and domid. This also improve security as the helper
performs various checks on frontend controlled entries.

Signed-off-by: Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
---
 tools/libxl/libxl.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index cb4a2a8..1d53cac 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1917,24 +1917,27 @@ libxl_device_vtpm *libxl_device_vtpm_list(libxl_ctx 
*ctx, uint32_t domid, int *n
 
     fe_path = libxl__sprintf(gc, "%s/device/vtpm", libxl__xs_get_dompath(gc, 
domid));
     dir = libxl__xs_directory(gc, XBT_NULL, fe_path, &ndirs);
-    if(dir) {
+    if(dir && ndirs) {
        vtpms = malloc(sizeof(*vtpms) * ndirs);
        libxl_device_vtpm* vtpm;
        libxl_device_vtpm* end = vtpms + ndirs;
        for(vtpm = vtpms; vtpm < end; ++vtpm, ++dir) {
           char* tmp;
-          const char* be_path = libxl__xs_read(gc, XBT_NULL,
-                GCSPRINTF("%s/%s/backend",
-                   fe_path, *dir));
+          const char* be_path;
+          int be_domid;
+
+          be_domid = libxl__get_backend_from_xs_fe(gc,
+                  GCSPRINTF("%s/%s", fe_path, *dir), &be_path);
+          if (be_domid < 0) {
+              free(vtpms);
+              return NULL;
+          }
 
           libxl_device_vtpm_init(vtpm);
 
           vtpm->devid = atoi(*dir);
 
-          tmp = libxl__xs_read(gc, XBT_NULL,
-                GCSPRINTF("%s/%s/backend-id",
-                   fe_path, *dir));
-          vtpm->backend_domid = atoi(tmp);
+          vtpm->backend_domid = be_domid;
 
           tmp = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/uuid", be_path));
           if (tmp) {
-- 
1.8.1.4


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