libxl: Do not trust backend for disk in getinfo

Do not read the frontend path out of the backend.  We have it in our
hand.  Likewise the guest (frontend) domid was one of our parameters (!)

This is part of XSA-178.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index a62594d5dd40871ba58a234936c609d7ba35b6e5..715ef49d2adcc00d78d9311867174c7255925b23 100644 (file)
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -2440,9 +2440,8 @@ int libxl_device_disk_getinfo(libxl_ctx *ctx, uint32_t domid,
     val = libxl__xs_read(gc, XBT_NULL, GCSPRINTF("%s/ring-ref", fe_path));
     diskinfo->rref = val ? strtoul(val, NULL, 10) : -1;
     diskinfo->frontend = xs_read(ctx->xsh, XBT_NULL,
-                                 libxl__sprintf(gc, "%s/frontend", diskinfo->backend), NULL);
-    val = libxl__xs_read(gc, XBT_NULL, libxl__sprintf(gc, "%s/frontend-id", diskinfo->backend));
-    diskinfo->frontend_id = val ? strtoul(val, NULL, 10) : -1;
+                                 GCSPRINTF("%s/frontend", libxl_path), NULL);
+    diskinfo->frontend_id = domid;
 
     GC_FREE;
     return 0;