tmem: By default to join an shared pool it must be authorized.

Having an off by default option allowing guests to join
_any_ shared pool is not very secure.

Lets eliminate tmem_shared_auth bootup option (which
was disabled by default) and have the code force this by default.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

docs/misc/tmem-internals.html

@@ -715,11 +715,9 @@ Ocfs2 has only very limited security; it is assumed that anyone who can
 access the filesystem bits on the shared disk can mount the filesystem and use
 it.  But in a virtualized data center,
 higher isolation requirements may apply.
-As a result, a Xen boot option -- "tmem_shared_auth" -- was
-added.  The option defaults to disabled,
-but when it is enabled, management tools must explicitly authenticate (or may
+As a result, management tools must explicitly authenticate (or may
 explicitly deny) shared pool access to any client.
-On Xen, this is done with the "xm
+On Xen, this is done with the "xl
 tmem-shared-auth" command.
 <P>
 <b><i>32-bit implementation</i>.</b>

docs/misc/xen-command-line.markdown

@@ -1539,9 +1539,6 @@ pages) must also be specified via the tbuf\_size parameter.
 ### tmem\_compress
 > `= <boolean>`
 
-### tmem\_shared\_auth
-> `= <boolean>`
-
 ### tsc
 > `= unstable | skewed | stable:socket`
 

xen/common/tmem.c

@@ -846,7 +846,6 @@ struct client *client_create(domid_t cli_id)
     client->info.version = TMEM_SPEC_VERSION;
     client->info.maxpools = MAX_POOLS_PER_DOMAIN;
     client->info.flags.u.compress = tmem_compression_enabled();
-    client->shared_auth_required = tmem_shared_auth();
     for ( i = 0; i < MAX_GLOBAL_SHARED_POOLS; i++)
         client->shared_auth_uuid[i][0] =
             client->shared_auth_uuid[i][1] = -1L;
@@ -1530,7 +1529,7 @@ int do_tmem_new_pool(domid_t this_cli_id,
             pool->shared = 0;
             goto out;
         }
-        if ( client->shared_auth_required && !tmem_global.shared_auth )
+        if ( !tmem_global.shared_auth )
         {
             for ( i = 0; i < MAX_GLOBAL_SHARED_POOLS; i++)
                 if ( (client->shared_auth_uuid[i][0] == uuid_lo) &&

xen/common/tmem_xen.c

@@ -20,9 +20,6 @@ boolean_param("tmem", opt_tmem);
 bool_t __read_mostly opt_tmem_compress = 0;
 boolean_param("tmem_compress", opt_tmem_compress);
 
-bool_t __read_mostly opt_tmem_shared_auth = 0;
-boolean_param("tmem_shared_auth", opt_tmem_shared_auth);
-
 atomic_t freeable_page_count = ATOMIC_INIT(0);
 
 /* these are a concurrency bottleneck, could be percpu and dynamically

xen/include/xen/tmem_xen.h

@@ -41,12 +41,6 @@ static inline bool_t tmem_compression_enabled(void)
     return opt_tmem_compress;
 }
 
-extern bool_t opt_tmem_shared_auth;
-static inline bool_t tmem_shared_auth(void)
-{
-    return opt_tmem_shared_auth;
-}
-
 #ifdef CONFIG_TMEM
 extern bool_t opt_tmem;
 static inline bool_t tmem_enabled(void)
@@ -291,7 +285,6 @@ struct client {
     long eph_count, eph_count_max;
     domid_t cli_id;
     xen_tmem_client_t info;
-    bool_t shared_auth_required;
     /* For save/restore/migration. */
     bool_t was_frozen;
     struct list_head persistent_invalidated_list;