[PATCH v1 1/4] tools/ocaml/libs/xb: do not crash after xenbus is unmapped

[Edwin Török <edvin.torok@xxxxxxxxxx>]

Xenmmap.unmap sets the address to MAP_FAILED in xenmmap_stubs.c.
If due to a bug there were still references to the Xenbus and we attempt
to use it then we crash.
Raise an exception instead of crashing.

(My initial version of fuzz testing had such a bug)

Signed-off-by: Edwin Török <edvin.torok@xxxxxxxxxx>
---
 tools/ocaml/libs/xb/xs_ring_stubs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/ocaml/libs/xb/xs_ring_stubs.c 
b/tools/ocaml/libs/xb/xs_ring_stubs.c
index 7537a23949..7a91fdee75 100644
--- a/tools/ocaml/libs/xb/xs_ring_stubs.c
+++ b/tools/ocaml/libs/xb/xs_ring_stubs.c
@@ -32,6 +32,7 @@
 #include <caml/fail.h>
 #include <caml/callback.h>
 
+#include <sys/mman.h>
 #include "mmap_stubs.h"
 
 #define GET_C_STRUCT(a) ((struct mmap_interface *) a)
@@ -166,6 +167,8 @@ CAMLprim value ml_interface_set_server_features(value 
interface, value v)
 {
        CAMLparam2(interface, v);
        struct xenstore_domain_interface *intf = GET_C_STRUCT(interface)->addr;
+       if (intf == (void*)MAP_FAILED)
+               caml_failwith("Interface closed");
 
        intf->server_features = Int_val(v);
 
-- 
2.29.2