s3:winbindd: make sure we remove pending io requests before closing client sockets

This avoids a crash inside the tevent epoll backend.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11141

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed May 20 22:16:54 CEST 2015 on sn-devel-104

(cherry picked from commit 435ddd8223eaa6fafb62cead0399bdd042d998e8)

2 files changed, 27 insertions, 0 deletions

diff --git a/source3/winbindd/winbindd.c b/source3/winbindd/winbindd.c
index caa9ed127dd..09ca27880c5 100644
--- a/source3/winbindd/winbindd.c
+++ b/source3/winbindd/winbindd.c
@@ -824,6 +824,7 @@ static void request_finished(struct winbindd_cli_state *state)
 		return;
 	}
 	tevent_req_set_callback(req, winbind_client_response_written, state);
+	state->io_req = req;
 }
 
 static void winbind_client_response_written(struct tevent_req *req)
@@ -833,6 +834,8 @@ static void winbind_client_response_written(struct tevent_req *req)
 	ssize_t ret;
 	int err;
 
+	state->io_req = NULL;
+
 	ret = wb_resp_write_recv(req, &err);
 	TALLOC_FREE(req);
 	if (ret == -1) {
@@ -859,6 +862,7 @@ static void winbind_client_response_written(struct tevent_req *req)
 		return;
 	}
 	tevent_req_set_callback(req, winbind_client_request_read, state);
+	state->io_req = req;
 }
 
 void request_error(struct winbindd_cli_state *state)
@@ -929,6 +933,7 @@ static void new_connection(int listen_sock, bool privileged)
 		return;
 	}
 	tevent_req_set_callback(req, winbind_client_request_read, state);
+	state->io_req = req;
 
 	/* Add to connection list */
 
@@ -942,6 +947,8 @@ static void winbind_client_request_read(struct tevent_req *req)
 	ssize_t ret;
 	int err;
 
+	state->io_req = NULL;
+
 	ret = wb_req_read_recv(req, state, &state->request, &err);
 	TALLOC_FREE(req);
 	if (ret == -1) {
@@ -973,6 +980,25 @@ static void remove_client(struct winbindd_cli_state *state)
 		return;
 	}
 
+	/*
+	 * We need to remove a pending wb_req_read_*
+	 * or wb_resp_write_* request before closing the
+	 * socket.
+	 *
+	 * This is important as they might have used tevent_add_fd() and we
+	 * use the epoll * backend on linux. So we must remove the tevent_fd
+	 * before closing the fd.
+	 *
+	 * Otherwise we might hit a race with close_conns_after_fork() (via
+	 * winbindd_reinit_after_fork()) where a file description
+	 * is still open in a child, which means it's still active in
+	 * the parents epoll queue, but the related tevent_fd is already
+	 * already gone in the parent.
+	 *
+	 * See bug #11141.
+	 */
+	TALLOC_FREE(state->io_req);
+
 	if (state->sock != -1) {
 		/* tell client, we are closing ... */
 		nwritten = write(state->sock, &c, sizeof(c));
diff --git a/source3/winbindd/winbindd.h b/source3/winbindd/winbindd.h
index db5dac8e3d9..d9adb96eefc 100644
--- a/source3/winbindd/winbindd.h
+++ b/source3/winbindd/winbindd.h
@@ -67,6 +67,7 @@ struct winbindd_cli_state {
 	struct winbindd_request *request;         /* Request from client */
 	struct tevent_queue *out_queue;
 	struct winbindd_response *response;        /* Respose to client */
+	struct tevent_req *io_req; /* wb_req_read_* or wb_resp_write_* */
 
 	struct getpwent_state *pwent_state; /* State for getpwent() */
 	struct getgrent_state *grent_state; /* State for getgrent() */