[Xen-changelog] [xen stable-4.6] libxl: Do not trust backend for vtpm in getinfo (except uuid)

[patchbot@xxxxxxx]

commit a08f74f621824e0fd23103fe97474cf032946ec5
Author:     Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
AuthorDate: Fri Apr 29 17:18:44 2016 +0100
Commit:     Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CommitDate: Mon Jun 6 14:47:35 2016 +0100

    libxl: Do not trust backend for vtpm in getinfo (except uuid)
    
    * Do not check the backend for existence.  We have already read the
      /libxl path so know that the vtpm exists (or is supposed to); if the
      backend doesn't exist then that must be the backend's doing.
    * Get the frontend path from the /libxl directory.
    * The frontend domid is the guest domid, and does not need to be read
      from xenstore (!)
    
    We still attempt to read the uuid from the backend.  This will be
    fixed in the next patch.
    
    This is part of XSA-178.
    
    Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxl/libxl.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index db92fae..e23f9bb 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -2261,9 +2261,6 @@ int libxl_device_vtpm_getinfo(libxl_ctx *ctx,
     if (!vtpminfo->backend) {
         goto err;
     }
-    if(!libxl__xs_read(gc, XBT_NULL, vtpminfo->backend)) {
-       goto err;
-    }
 
     rc = libxl__backendpath_parse_domid(gc, vtpminfo->backend,
                                         &vtpminfo->backend_id);
@@ -2282,11 +2279,8 @@ int libxl_device_vtpm_getinfo(libxl_ctx *ctx,
     vtpminfo->rref = val ? strtoul(val, NULL, 10) : -1;
 
     vtpminfo->frontend = xs_read(ctx->xsh, XBT_NULL,
-          GCSPRINTF("%s/frontend", vtpminfo->backend), NULL);
-
-    val = libxl__xs_read(gc, XBT_NULL,
-          GCSPRINTF("%s/frontend-id", vtpminfo->backend));
-    vtpminfo->frontend_id = val ? strtoul(val, NULL, 10) : -1;
+          GCSPRINTF("%s/frontend", libxl_path), NULL);
+    vtpminfo->frontend_id = domid;
 
     val = libxl__xs_read(gc, XBT_NULL,
           GCSPRINTF("%s/uuid", vtpminfo->backend));
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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