2 files changed, 9 insertions, 0 deletions

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index b3b8f2f3ad10..6f0121e3be69 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -810,6 +810,12 @@ static int process_msg(void)
                 goto out;
         }
 
+        if (msg->hdr.len > XENSTORE_PAYLOAD_MAX) {
+                kfree(msg);
+                err = -EINVAL;
+                goto out;
+        }
+
         body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH);
         if (body == NULL) {
                 kfree(msg);
diff --git a/include/xen/interface/io/xs_wire.h b/include/xen/interface/io/xs_wire.h
index f0b6890370be..3c1877caaefc 100644
--- a/include/xen/interface/io/xs_wire.h
+++ b/include/xen/interface/io/xs_wire.h
@@ -88,4 +88,7 @@ struct xenstore_domain_interface {
     XENSTORE_RING_IDX rsp_cons, rsp_prod;
 };
 
+/* Violating this is very bad.  See docs/misc/xenstore.txt. */
+#define XENSTORE_PAYLOAD_MAX 4096
+
 #endif /* _XS_WIRE_H */