messaging3: Protect messaging_dgm against multiple contexts

We can't rely on posix locking within a process

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

diff --git a/source3/lib/messages_dgm.c b/source3/lib/messages_dgm.c
index dee1f6476b1fa3adb443c52460651e829c44aa16..e95aa9530df3371b0c18b654e6c957138b685d06 100644 (file)
--- a/source3/lib/messages_dgm.c
+++ b/source3/lib/messages_dgm.c
@@ -40,6 +40,8 @@ struct messaging_dgm_context {
                        const uint8_t *msg, size_t msg_len,
                        void *private_data);
        void *recv_cb_private_data;
+
+       bool *have_dgm_context;
 };
 
 struct messaging_dgm_hdr {
@@ -187,6 +189,11 @@ int messaging_dgm_init(TALLOC_CTX *mem_ctx,
        struct sockaddr_un socket_address;
        size_t sockname_len;
        uint64_t cookie;
+       static bool have_dgm_context = false;
+
+       if (have_dgm_context) {
+               return EEXIST;
+       }
 
        ctx = talloc_zero(mem_ctx, struct messaging_dgm_context);
        if (ctx == NULL) {
@@ -255,6 +262,8 @@ int messaging_dgm_init(TALLOC_CTX *mem_ctx,
        }
        talloc_set_destructor(ctx, messaging_dgm_context_destructor);
 
+       ctx->have_dgm_context = &have_dgm_context;
+
        *pctx = ctx;
        return 0;
 
@@ -277,6 +286,11 @@ static int messaging_dgm_context_destructor(struct messaging_dgm_context *c)
                (void)messaging_dgm_lockfile_remove(c, c->cache_dir, pid.pid);
        }
        close(c->lockfile_fd);
+
+       if (c->have_dgm_context != NULL) {
+               *c->have_dgm_context = false;
+       }
+
        return 0;
 }