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 4ed9cc6edc8931061e2cc52fa97964f6bb4d7969..46f2e9e3343d0b36b45c919bf2755294fd281ff9 100644 (file)
--- 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 909991ed27c6f1ada4a04426e396d232d126df8e..7a41d4de51d4e4744172dd9e235cb29640bd50de 100644 (file)
--- 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) {