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

diff --git a/source3/winbindd/winbindd.c b/source3/winbindd/winbindd.c
index 87bc5324272dc743668d949fc9c3672b376aa465..4ffe79c41fa4b5c8e3d65e19515b37d03e36f3d2 100644 (file)
--- 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 f676b1e317af375f4e9276fcaf8d8a59d6a6597a..b2105e370cc1d92475ba55da3100c80b0f4f6219 100644 (file)
--- 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() */