[Xen-devel] [PATCH RFC 06/12] libxl: set correct permissions for the full backend path

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

The backend path should be fully owned by the domain where it resides.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 tools/libxl/libxl_device.c   |   45 +++++++++++++++++++++++++++++++++++++++--
 tools/libxl/libxl_internal.h |    2 +
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 082bd2a..f39b7b1 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -83,6 +83,47 @@ out:
     return rc;
 }
 
+int libxl__create_backend_path(libxl__gc *gc, xs_transaction_t t,
+                               libxl__device *device)
+{
+    char *dom_backend_path;
+    char *be_path = libxl__device_backend_path(gc, device);
+    char *p;
+    struct xs_permissions backend_dir_perms[2];
+    struct xs_permissions backend_path_perms[1];
+    int rc;
+
+    backend_path_perms[0].id = device->backend_domid;
+    backend_path_perms[0].perms = XS_PERM_NONE;
+
+    backend_dir_perms[0].id = device->backend_domid;
+    backend_dir_perms[0].perms = XS_PERM_NONE;
+    backend_dir_perms[1].id = device->domid;
+    backend_dir_perms[1].perms = XS_PERM_READ;
+
+    rc = libxl__xs_rm_checked(gc, t, be_path);
+    if (rc) goto error;
+    if (!libxl__xs_mkdir(gc, t, be_path, backend_dir_perms,
+        ARRAY_SIZE(backend_dir_perms)))
+        goto error;
+
+    dom_backend_path = GCSPRINTF("%s/backend",
+                            libxl__xs_get_dompath(gc, device->backend_domid));
+    while (strcmp(be_path, dom_backend_path) != 0) {
+        p = strrchr(be_path, '/');
+        if (!p) goto error;
+        *p = '\0';
+
+        xs_set_permissions(CTX->xsh, t, be_path, backend_path_perms,
+                           ARRAY_SIZE(backend_path_perms));
+    }
+
+    return 0;
+
+error:
+    return ERROR_FAIL;
+}
+
 int libxl__device_generic_add(libxl__gc *gc, xs_transaction_t t,
         libxl__device *device, char **bents, char **fents, char **ro_fents)
 {
@@ -135,9 +176,7 @@ retry_transaction:
     }
 
     if (bents) {
-        xs_rm(ctx->xsh, t, backend_path);
-        xs_mkdir(ctx->xsh, t, backend_path);
-        xs_set_permissions(ctx->xsh, t, backend_path, backend_perms, 
ARRAY_SIZE(backend_perms));
+        libxl__create_backend_path(gc, t, device);
         xs_write(ctx->xsh, t, libxl__sprintf(gc, "%s/frontend", backend_path), 
frontend_path, strlen(frontend_path));
         libxl__xs_writev(gc, t, backend_path, bents);
     }
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 3b74726..1746b7d 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -929,6 +929,8 @@ _hidden int libxl__domain_pvcontrol_write(libxl__gc *gc, 
xs_transaction_t t,
 _hidden char *libxl__device_disk_string_of_backend(libxl_disk_backend backend);
 _hidden char *libxl__device_disk_string_of_format(libxl_disk_format format);
 _hidden int libxl__device_disk_set_backend(libxl__gc*, libxl_device_disk*);
+_hidden int libxl__create_backend_path(libxl__gc *gc, xs_transaction_t t,
+                                       libxl__device *device);
 
 _hidden int libxl__device_physdisk_major_minor(const char *physpath, int 
*major, int *minor);
 _hidden int libxl__device_disk_dev_number(const char *virtpath,
-- 
1.7.7.5 (Apple Git-26)


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