From: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Date: Mon, 2 Mar 2020 19:21:33 +0000 (-0500)
Subject: Fix: set FD_CLOEXEC on incoming FDs.
X-Git-Tag: v2.11.1~1
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=fe61d8ce58eb511477eb9cbf5719fd73f242538f;p=lttng-ust.git

Fix: set FD_CLOEXEC on incoming FDs.

The stream shm FDs are allocated by the consumer process, and then
passed to the applications over unix sockets. When opening those
file descriptors on reception, the FD_CLOEXEC flag is not set.

In a fork + exec scenario, parent process streams shm FDs and channel
wake FDs are present in the resulting child process.

Set FD_CLOEXEC on reception (ustcomm_recv_fds_unix_sock) to
prevent such scenario.

Change-Id: Id58077b272be9c1ab239846639ffd8103b3d50f1
Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/liblttng-ust-comm/lttng-ust-comm.c b/liblttng-ust-comm/lttng-ust-comm.c
index 4ed9cc6e..46f2e9e3 100644
--- a/liblttng-ust-comm/lttng-ust-comm.c
+++ b/liblttng-ust-comm/lttng-ust-comm.c
@@ -106,6 +106,7 @@ int ustcomm_connect_unix_sock(const char *pathname, long timeout)
 	/*
 	 * libust threads require the close-on-exec flag for all
 	 * resources so it does not leak file descriptors upon exec.
+	 * SOCK_CLOEXEC is not used since it is linux specific.
 	 */
 	fd = socket(PF_UNIX, SOCK_STREAM, 0);
 	if (fd < 0) {
@@ -451,6 +452,7 @@ ssize_t ustcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
 	char recv_fd[CMSG_SPACE(sizeof_fds)];
 	struct msghdr msg;
 	char dummy;
+	int i;
 
 	memset(&msg, 0, sizeof(msg));
 
@@ -506,7 +508,18 @@ ssize_t ustcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
 		ret = -1;
 		goto end;
 	}
+
 	memcpy(fds, CMSG_DATA(cmsg), sizeof_fds);
+
+	/* Set FD_CLOEXEC */
+	for (i = 0; i < nb_fd; i++) {
+		ret = fcntl(fds[i], F_SETFD, FD_CLOEXEC);
+		if (ret < 0) {
+			PERROR("fcntl failed to set FD_CLOEXEC on fd %d",
+			       fds[i]);
+		}
+	}
+
 	ret = nb_fd;
 end:
 	return ret;
diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index 909991ed..7a41d4de 100644
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -328,11 +328,6 @@ struct shm_object *shm_object_table_append_shm(struct shm_object_table *table,
 	obj->shm_fd = shm_fd;
 	obj->shm_fd_ownership = 1;
 
-	ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC);
-	if (ret < 0) {
-		PERROR("fcntl");
-		goto error_fcntl;
-	}
 	/* The write end of the pipe needs to be non-blocking */
 	ret = fcntl(obj->wait_fd[1], F_SETFL, O_NONBLOCK);
 	if (ret < 0) {