[PATCH 27/28] libxl: Limit qemu physmap entries

[Ian Jackson <ian.jackson@eu.citrix.com>]

Add a maximum limit of physmap entries to save, so that when the guest
gets write access to physmap it cannot DOS the toolstack.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
v6: Split out of xs permissions relaxation patch.
---
 tools/libxl/libxl_dom.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 6ded9c1..60e8f7f 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -1431,6 +1431,8 @@ static void append_string(libxl__gc *gc, char **buf, uint32_t *len,
     *len += extralen;
 }
 
+#define MAX_PHYSMAP_ENTRIES 12
+
 int libxl__save_emulator_xenstore_data(libxl__domain_suspend_state *dss,
                                        char **callee_buf,
                                        uint32_t *callee_len)
@@ -1450,6 +1452,11 @@ int libxl__save_emulator_xenstore_data(libxl__domain_suspend_state *dss,
                                   &nr_entries);
     if (!entries || nr_entries == 0) { rc = 0; goto out; }
 
+    if (nr_entries > MAX_PHYSMAP_ENTRIES) {
+        LOG(ERROR, "Max physmap entries reached");
+        return ERROR_FAIL;
+    }
+
     for (i = 0; i < nr_entries; ++i) {
         static const char *const physmap_subkeys[] = {
             "start_addr", "size", "name"
-- 
1.7.10.4