[Xen-devel] [PULL 08/21] xen: additionally restrict xenforeignmemory operations

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

From: Paul Durrant <paul.durrant@xxxxxxxxxx>

Commit f0f272baf3a7 "xen: use libxendevice model to restrict operations"
added a command-line option (-xen-domid-restrict) to limit operations
using the libxendevicemodel API to a specified domid. The commit also
noted that the restriction would be extended to cover operations issued
via other xen libraries by subsequent patches.

My recent Xen patch [1] added a call to the xenforeignmemory API to allow
it to be restricted. This patch now makes use of that new call when the
-xen-domid-restrict option is passed.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=5823d6eb

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 include/hw/xen/xen_common.h | 134 ++++++++++++++++++++++++++------------------
 1 file changed, 78 insertions(+), 56 deletions(-)

diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 0fcbba8..e00ddd7 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -26,6 +26,58 @@ extern xc_interface *xen_xc;
  * We don't support Xen prior to 4.2.0.
  */
 
+/* Xen 4.2 through 4.6 */
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40701
+
+typedef xc_interface xenforeignmemory_handle;
+typedef xc_evtchn xenevtchn_handle;
+typedef xc_gnttab xengnttab_handle;
+
+#define xenevtchn_open(l, f) xc_evtchn_open(l, f);
+#define xenevtchn_close(h) xc_evtchn_close(h)
+#define xenevtchn_fd(h) xc_evtchn_fd(h)
+#define xenevtchn_pending(h) xc_evtchn_pending(h)
+#define xenevtchn_notify(h, p) xc_evtchn_notify(h, p)
+#define xenevtchn_bind_interdomain(h, d, p) xc_evtchn_bind_interdomain(h, d, p)
+#define xenevtchn_unmask(h, p) xc_evtchn_unmask(h, p)
+#define xenevtchn_unbind(h, p) xc_evtchn_unbind(h, p)
+
+#define xengnttab_open(l, f) xc_gnttab_open(l, f)
+#define xengnttab_close(h) xc_gnttab_close(h)
+#define xengnttab_set_max_grants(h, n) xc_gnttab_set_max_grants(h, n)
+#define xengnttab_map_grant_ref(h, d, r, p) xc_gnttab_map_grant_ref(h, d, r, p)
+#define xengnttab_unmap(h, a, n) xc_gnttab_munmap(h, a, n)
+#define xengnttab_map_grant_refs(h, c, d, r, p) \
+    xc_gnttab_map_grant_refs(h, c, d, r, p)
+#define xengnttab_map_domain_grant_refs(h, c, d, r, p) \
+    xc_gnttab_map_domain_grant_refs(h, c, d, r, p)
+
+#define xenforeignmemory_open(l, f) xen_xc
+#define xenforeignmemory_close(h)
+
+static inline void *xenforeignmemory_map(xc_interface *h, uint32_t dom,
+                                         int prot, size_t pages,
+                                         const xen_pfn_t arr[/*pages*/],
+                                         int err[/*pages*/])
+{
+    if (err)
+        return xc_map_foreign_bulk(h, dom, prot, arr, err, pages);
+    else
+        return xc_map_foreign_pages(h, dom, prot, arr, pages);
+}
+
+#define xenforeignmemory_unmap(h, p, s) munmap(p, s * XC_PAGE_SIZE)
+
+#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40701 */
+
+#include <xenevtchn.h>
+#include <xengnttab.h>
+#include <xenforeignmemory.h>
+
+#endif
+
+extern xenforeignmemory_handle *xen_fmem;
+
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
 
 typedef xc_interface xendevicemodel_handle;
@@ -158,6 +210,13 @@ static inline int xendevicemodel_restrict(
     return -1;
 }
 
+static inline int xenforeignmemory_restrict(
+    xenforeignmemory_handle *fmem, domid_t domid)
+{
+    errno = ENOTTY;
+    return -1;
+}
+
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
 
 #undef XC_WANT_COMPAT_DEVICEMODEL_API
@@ -215,69 +274,32 @@ static inline int xen_modified_memory(domid_t domid, 
uint64_t first_pfn,
 
 static inline int xen_restrict(domid_t domid)
 {
-    int rc = xendevicemodel_restrict(xen_dmod, domid);
+    int rc;
 
-    trace_xen_domid_restrict(errno);
+    /* Attempt to restrict devicemodel operations */
+    rc = xendevicemodel_restrict(xen_dmod, domid);
+    trace_xen_domid_restrict(rc ? errno : 0);
 
-    if (errno == ENOTTY) {
-        return 0;
+    if (rc < 0) {
+        /*
+         * If errno is ENOTTY then restriction is not implemented so
+         * there's no point in trying to restrict other types of
+         * operation, but it should not be treated as a failure.
+         */
+        if (errno == ENOTTY) {
+            return 0;
+        }
+
+        return rc;
     }
 
-    return rc;
-}
-
-/* Xen 4.2 through 4.6 */
-#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40701
-
-typedef xc_interface xenforeignmemory_handle;
-typedef xc_evtchn xenevtchn_handle;
-typedef xc_gnttab xengnttab_handle;
-
-#define xenevtchn_open(l, f) xc_evtchn_open(l, f);
-#define xenevtchn_close(h) xc_evtchn_close(h)
-#define xenevtchn_fd(h) xc_evtchn_fd(h)
-#define xenevtchn_pending(h) xc_evtchn_pending(h)
-#define xenevtchn_notify(h, p) xc_evtchn_notify(h, p)
-#define xenevtchn_bind_interdomain(h, d, p) xc_evtchn_bind_interdomain(h, d, p)
-#define xenevtchn_unmask(h, p) xc_evtchn_unmask(h, p)
-#define xenevtchn_unbind(h, p) xc_evtchn_unbind(h, p)
-
-#define xengnttab_open(l, f) xc_gnttab_open(l, f)
-#define xengnttab_close(h) xc_gnttab_close(h)
-#define xengnttab_set_max_grants(h, n) xc_gnttab_set_max_grants(h, n)
-#define xengnttab_map_grant_ref(h, d, r, p) xc_gnttab_map_grant_ref(h, d, r, p)
-#define xengnttab_unmap(h, a, n) xc_gnttab_munmap(h, a, n)
-#define xengnttab_map_grant_refs(h, c, d, r, p) \
-    xc_gnttab_map_grant_refs(h, c, d, r, p)
-#define xengnttab_map_domain_grant_refs(h, c, d, r, p) \
-    xc_gnttab_map_domain_grant_refs(h, c, d, r, p)
-
-#define xenforeignmemory_open(l, f) xen_xc
-#define xenforeignmemory_close(h)
+    /* Restrict foreignmemory operations */
+    rc = xenforeignmemory_restrict(xen_fmem, domid);
+    trace_xen_domid_restrict(rc ? errno : 0);
 
-static inline void *xenforeignmemory_map(xc_interface *h, uint32_t dom,
-                                         int prot, size_t pages,
-                                         const xen_pfn_t arr[/*pages*/],
-                                         int err[/*pages*/])
-{
-    if (err)
-        return xc_map_foreign_bulk(h, dom, prot, arr, err, pages);
-    else
-        return xc_map_foreign_pages(h, dom, prot, arr, pages);
+    return rc;
 }
 
-#define xenforeignmemory_unmap(h, p, s) munmap(p, s * XC_PAGE_SIZE)
-
-#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40701 */
-
-#include <xenevtchn.h>
-#include <xengnttab.h>
-#include <xenforeignmemory.h>
-
-#endif
-
-extern xenforeignmemory_handle *xen_fmem;
-
 void destroy_hvm_domain(bool reboot);
 
 /* shutdown/destroy current domain because of an error */
-- 
1.9.1


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