runcmd: use a pipe for stdin to child processes

this allows child processes to detect the exit of the parent by
looking for EOF on stdin

1 files changed, 46 insertions, 7 deletions

diff --git a/lib/util/util_runcmd.c b/lib/util/util_runcmd.c
index cfe0034a32f..8a475ef301d 100644
--- a/lib/util/util_runcmd.c
+++ b/lib/util/util_runcmd.c
@@ -33,9 +33,10 @@
 struct samba_runcmd_state {
 	int stdout_log_level;
 	int stderr_log_level;
+	struct tevent_fd *fde_stdin;
 	struct tevent_fd *fde_stdout;
 	struct tevent_fd *fde_stderr;
-	int fd_stdout, fd_stderr;
+	int fd_stdin, fd_stdout, fd_stderr;
 	char *arg0;
 	pid_t pid;
 	char buf[1024];
@@ -72,7 +73,7 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 {
 	struct tevent_req *req;
 	struct samba_runcmd_state *state;
-	int p1[2], p2[2];
+	int p1[2], p2[2], p3[2];
 	char **argv;
 	va_list ap;
 
@@ -100,6 +101,14 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 		tevent_req_error(req, errno);
 		return tevent_req_post(req, ev);
 	}
+	if (pipe(p3) != 0) {
+		close(p1[0]);
+		close(p1[1]);
+		close(p2[0]);
+		close(p2[1]);
+		tevent_req_error(req, errno);
+		return tevent_req_post(req, ev);
+	}
 
 	state->pid = fork();
 	if (state->pid == (pid_t)-1) {
@@ -107,6 +116,8 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 		close(p1[1]);
 		close(p2[0]);
 		close(p2[1]);
+		close(p3[0]);
+		close(p3[1]);
 		tevent_req_error(req, errno);
 		return tevent_req_post(req, ev);
 	}
@@ -115,10 +126,14 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 		/* the parent */
 		close(p1[1]);
 		close(p2[1]);
+		close(p3[0]);
 		state->fd_stdout = p1[0];
 		state->fd_stderr = p2[0];
+		state->fd_stdin  = p3[1];
+
 		set_blocking(state->fd_stdout, false);
 		set_blocking(state->fd_stderr, false);
+		set_blocking(state->fd_stdin,  false);
 
 		talloc_set_destructor(state, samba_runcmd_state_destructor);
 
@@ -128,8 +143,9 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 						  samba_runcmd_io_handler,
 						  req);
 		if (tevent_req_nomem(state->fde_stdout, req)) {
-			close(p1[0]);
-			close(p2[0]);
+			close(state->fd_stdout);
+			close(state->fd_stderr);
+			close(state->fd_stdin);
 			return tevent_req_post(req, ev);
 		}
 		tevent_fd_set_auto_close(state->fde_stdout);
@@ -140,11 +156,23 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 						  samba_runcmd_io_handler,
 						  req);
 		if (tevent_req_nomem(state->fde_stdout, req)) {
-			close(p2[0]);
+			close(state->fd_stderr);
+			close(state->fd_stdin);
 			return tevent_req_post(req, ev);
 		}
 		tevent_fd_set_auto_close(state->fde_stderr);
 
+		state->fde_stdin = tevent_add_fd(ev, state,
+						 state->fd_stdin,
+						 0,
+						 samba_runcmd_io_handler,
+						 req);
+		if (tevent_req_nomem(state->fde_stdin, req)) {
+			close(state->fd_stdin);
+			return tevent_req_post(req, ev);
+		}
+		tevent_fd_set_auto_close(state->fde_stdin);
+
 		if (!timeval_is_zero(&endtime)) {
 			tevent_req_set_endtime(req, ev, endtime);
 		}
@@ -155,6 +183,7 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 	/* the child */
 	close(p1[0]);
 	close(p2[0]);
+	close(p3[1]);
 	close(0);
 	close(1);
 	close(2);
@@ -164,7 +193,7 @@ struct tevent_req *samba_runcmd_send(TALLOC_CTX *mem_ctx,
 	tevent_re_initialise(ev);
 
 	/* setup for logging to go to the parents debug log */
-	open("/dev/null", O_RDONLY); /* for stdin */
+	dup2(p3[0], 0);
 	dup2(p1[1], 1);
 	dup2(p2[1], 2);
 
@@ -211,9 +240,19 @@ static void samba_runcmd_io_handler(struct tevent_context *ev,
 	if (fde == state->fde_stdout) {
 		level = state->stdout_log_level;
 		fd = state->fd_stdout;
-	} else {
+	} else if (fde == state->fde_stderr) {
 		level = state->stderr_log_level;
 		fd = state->fd_stderr;
+	} else if (fde == state->fde_stdin) {
+		char c;
+		if (read(state->fd_stdin, &c, 1) != 1) {
+			/* the child has closed its stdin */
+			talloc_free(fde);
+			state->fde_stdin = NULL;
+			return;
+		}
+	} else {
+		return;
 	}
 
 	if (!(flags & TEVENT_FD_READ)) {