[xen stable-4.11] xen/xsm: Add new SILO mode for XSM

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[xen stable-4.11] xen/xsm: Add new SILO mode for XSM

patchbot
commit b415a99d538bac50e034092c59733810cc245674
Author:     Xin Li <[hidden email]>
AuthorDate: Tue Oct 9 17:33:20 2018 +0800
Commit:     Julien Grall <[hidden email]>
CommitDate: Fri Jun 14 14:38:40 2019 +0100

    xen/xsm: Add new SILO mode for XSM
   
    When SILO is enabled, there would be no page-sharing or event notifications
    between unprivileged VMs (no grant tables or event channels).
   
    Signed-off-by: Xin Li <[hidden email]>
    Acked-by: Daniel De Graaf <[hidden email]>
    Acked-by: Andrew Cooper <[hidden email]>
---
 docs/misc/xen-command-line.markdown |   5 +-
 xen/common/Kconfig                  |  15 +++++
 xen/include/xsm/dummy.h             |   3 +-
 xen/include/xsm/xsm.h               |   6 ++
 xen/xsm/Makefile                    |   1 +
 xen/xsm/silo.c                      | 108 ++++++++++++++++++++++++++++++++++++
 xen/xsm/xsm_core.c                  |  11 ++++
 7 files changed, 147 insertions(+), 2 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index 1025fb8a6b..c63a07d29b 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -866,7 +866,7 @@ Note that specifying zero as domU value means zero, while for dom0 it means
 to use the default.
 
 ### xsm
-> `= dummy | flask`
+> `= dummy | flask | silo`
 
 > Default: `dummy`
 
@@ -877,6 +877,9 @@ the hypervisor was compiled with XSM support.
   (the dummy module) will be applied.  It's also used when XSM is compiled out.
 * `flask`: this is the policy based access control.  To choose this, the
   separated option in kconfig must also be enabled.
+* `silo`: this will deny any unmediated communication channels between
+  unprivileged VMs.  To choose this, the separated option in kconfig must also
+  be enabled.
 
 ### flask
 > `= permissive | enforcing | late | disabled`
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 448c2888fe..512f6446a3 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -143,15 +143,30 @@ config XSM_POLICY
 
   If unsure, say Y.
 
+config XSM_SILO
+ def_bool y
+ prompt "SILO support"
+ depends on XSM
+ ---help---
+  Enables SILO as the access control mechanism used by the XSM framework.
+  This is not the default module, add boot parameter xsm=silo to choose
+  it. This will deny any unmediated communication channels (grant tables
+  and event channels) between unprivileged VMs.
+
+  If unsure, say Y.
+
 choice
  prompt "Default XSM implementation"
  depends on XSM
  default XSM_FLASK_DEFAULT if XSM_FLASK
+ default XSM_SILO_DEFAULT if XSM_SILO
  default XSM_DUMMY_DEFAULT
  config XSM_DUMMY_DEFAULT
  bool "Match non-XSM behavior"
  config XSM_FLASK_DEFAULT
  bool "FLux Advanced Security Kernel" if XSM_FLASK
+ config XSM_SILO_DEFAULT
+ bool "SILO" if XSM_SILO
 endchoice
 
 config LATE_HWDOM
diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index ff6b2dbf39..a507fa43f5 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -48,7 +48,8 @@ void __xsm_action_mismatch_detected(void);
  * There is no xsm_default_t argument available, so the value from the assertion
  * is used to initialize the variable.
  */
-#define XSM_INLINE /* */
+#define XSM_INLINE __maybe_unused
+
 #define XSM_DEFAULT_ARG /* */
 #define XSM_DEFAULT_VOID void
 #define XSM_ASSERT_ACTION(def) xsm_default_t action = def; (void)action
diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
index f0c6fc7e29..b16a1b5b18 100644
--- a/xen/include/xsm/xsm.h
+++ b/xen/include/xsm/xsm.h
@@ -733,6 +733,12 @@ extern const unsigned char xsm_init_policy[];
 extern const unsigned int xsm_init_policy_size;
 #endif
 
+#ifdef CONFIG_XSM_SILO
+extern void silo_init(void);
+#else
+static inline void silo_init(void) {}
+#endif
+
 #else /* CONFIG_XSM */
 
 #include <xsm/dummy.h>
diff --git a/xen/xsm/Makefile b/xen/xsm/Makefile
index 3252c46e64..50e21303b3 100644
--- a/xen/xsm/Makefile
+++ b/xen/xsm/Makefile
@@ -1,5 +1,6 @@
 obj-y += xsm_core.o
 obj-$(CONFIG_XSM) += xsm_policy.o
 obj-$(CONFIG_XSM) += dummy.o
+obj-$(CONFIG_XSM_SILO) += silo.o
 
 subdir-$(CONFIG_FLASK) += flask
diff --git a/xen/xsm/silo.c b/xen/xsm/silo.c
new file mode 100644
index 0000000000..4850756a3d
--- /dev/null
+++ b/xen/xsm/silo.c
@@ -0,0 +1,108 @@
+/******************************************************************************
+ * xsm/silo.c
+ *
+ * SILO module for XSM (Xen Security Modules)
+ *
+ * Copyright (c) 2018 Citrix Systems Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; If not, see <http://www.gnu.org/licenses/>.
+ */
+#define XSM_NO_WRAPPERS
+#include <xsm/dummy.h>
+
+/*
+ * Check if inter-domain communication is allowed.
+ * Return true when pass check.
+ */
+static bool silo_mode_dom_check(const struct domain *ldom,
+                                const struct domain *rdom)
+{
+    const struct domain *currd = current->domain;
+
+    return (is_control_domain(currd) || is_control_domain(ldom) ||
+            is_control_domain(rdom) || ldom == rdom);
+}
+
+static int silo_evtchn_unbound(struct domain *d1, struct evtchn *chn,
+                               domid_t id2)
+{
+    int rc = -EPERM;
+    struct domain *d2 = rcu_lock_domain_by_any_id(id2);
+
+    if ( d2 == NULL )
+        rc = -ESRCH;
+    else
+    {
+        if ( silo_mode_dom_check(d1, d2) )
+            rc = xsm_evtchn_unbound(d1, chn, id2);
+        rcu_unlock_domain(d2);
+    }
+
+    return rc;
+}
+
+static int silo_evtchn_interdomain(struct domain *d1, struct evtchn *chan1,
+                                   struct domain *d2, struct evtchn *chan2)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_evtchn_interdomain(d1, chan1, d2, chan2);
+    return -EPERM;
+}
+
+static int silo_grant_mapref(struct domain *d1, struct domain *d2,
+                             uint32_t flags)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_grant_mapref(d1, d2, flags);
+    return -EPERM;
+}
+
+static int silo_grant_transfer(struct domain *d1, struct domain *d2)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_grant_transfer(d1, d2);
+    return -EPERM;
+}
+
+static int silo_grant_copy(struct domain *d1, struct domain *d2)
+{
+    if ( silo_mode_dom_check(d1, d2) )
+        return xsm_grant_copy(d1, d2);
+    return -EPERM;
+}
+
+static struct xsm_operations silo_xsm_ops = {
+    .evtchn_unbound = silo_evtchn_unbound,
+    .evtchn_interdomain = silo_evtchn_interdomain,
+    .grant_mapref = silo_grant_mapref,
+    .grant_transfer = silo_grant_transfer,
+    .grant_copy = silo_grant_copy,
+};
+
+void __init silo_init(void)
+{
+    printk("Initialising XSM SILO mode\n");
+
+    if ( register_xsm(&silo_xsm_ops) )
+        panic("SILO: Unable to register with XSM\n");
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/xsm/xsm_core.c b/xen/xsm/xsm_core.c
index e2f17e4b41..7b862ea79d 100644
--- a/xen/xsm/xsm_core.c
+++ b/xen/xsm/xsm_core.c
@@ -34,11 +34,14 @@ struct xsm_operations *xsm_ops;
 enum xsm_bootparam {
     XSM_BOOTPARAM_DUMMY,
     XSM_BOOTPARAM_FLASK,
+    XSM_BOOTPARAM_SILO,
 };
 
 static enum xsm_bootparam __initdata xsm_bootparam =
 #ifdef CONFIG_XSM_FLASK_DEFAULT
     XSM_BOOTPARAM_FLASK;
+#elif CONFIG_XSM_SILO_DEFAULT
+    XSM_BOOTPARAM_SILO;
 #else
     XSM_BOOTPARAM_DUMMY;
 #endif
@@ -53,6 +56,10 @@ static int __init parse_xsm_param(const char *s)
     else if ( !strcmp(s, "flask") )
         xsm_bootparam = XSM_BOOTPARAM_FLASK;
 #endif
+#ifdef CONFIG_XSM_SILO
+    else if ( !strcmp(s, "silo") )
+        xsm_bootparam = XSM_BOOTPARAM_SILO;
+#endif
     else
         rc = -EINVAL;
 
@@ -96,6 +103,10 @@ static int __init xsm_core_init(const void *policy_buffer, size_t policy_size)
         flask_init(policy_buffer, policy_size);
         break;
 
+    case XSM_BOOTPARAM_SILO:
+        silo_init();
+        break;
+
     default:
         ASSERT_UNREACHABLE();
         break;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.11

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