From: Edwin Török <edvin.torok@citrix.com>
Date: Fri, 15 Jan 2021 18:23:10 +0000 (+0000)
Subject: tools/ocaml/libs/xb: Do not crash after xenbus is unmapped
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=f66542f5d2217f3868d78ff64d11a2a02674fed9;p=xen.git

tools/ocaml/libs/xb: Do not crash after xenbus is unmapped

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.

Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
(cherry picked from commit 5e317896342d553f0b55f72948bbf93a0f1147d3)
---

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);