xen/xsm: flask: restore sidtab state on policy load failure

Error path of failed sidtab_map() leaves global sidtab in shutdown state and
from that point system is unable to allocate new SIDs in sidtab_context_to_sid().
To restore sidtab state new function sidtab_cancel_shutdown() is introduced,
which only resets shutdown flag, rewinding effect of sidtab_shutdown().

Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
Acked-by: Daniel P. Smith <dpsmith@apertussoutions.com>

xen/xsm/flask/ss/services.c

@@ -1428,6 +1428,7 @@ int security_load_policy(const void *data, size_t len)
     if ( sidtab_map(&sidtab, clone_sid, &newsidtab) )
     {
         rc = -ENOMEM;
+        sidtab_cancel_shutdown(&sidtab);
         goto err;
     }
 

xen/xsm/flask/ss/sidtab.c

@@ -320,3 +320,10 @@ void sidtab_shutdown(struct sidtab *s)
     s->shutdown = 1;
     SIDTAB_UNLOCK(s);
 }
+
+void sidtab_cancel_shutdown(struct sidtab *s)
+{
+    SIDTAB_LOCK(s);
+    s->shutdown = 0;
+    SIDTAB_UNLOCK(s);
+}

xen/xsm/flask/ss/sidtab.h

@@ -49,5 +49,6 @@ void sidtab_hash_eval(struct sidtab *h, char *tag);
 void sidtab_destroy(struct sidtab *s);
 void sidtab_set(struct sidtab *dst, struct sidtab *src);
 void sidtab_shutdown(struct sidtab *s);
+void sidtab_cancel_shutdown(struct sidtab *s);
 
 #endif    /* _SS_SIDTAB_H_ */