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 5b9cb85381fcb815998c7ecaa733a52a7d2a31e7..814ccde17954b82200242e4ec03304907c2fac5c 100644 (file)
--- a/liblttng-ust-comm/lttng-ust-comm.c
+++ b/liblttng-ust-comm/lttng-ust-comm.c
@@ -107,6 +107,7 @@ 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) {
@@ -452,6 +453,7 @@ 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));
 
@@ -507,7 +509,18 @@ 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 44a830af20446142f8e21177b5187e8dfd6d4af0..461befb99db5ed45cde5dcdcfecb860df06003b3 100644 (file)
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -329,11 +329,6 @@ 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) {