android/sw_sync: use get_unused_fd_flags(O_CLOEXEC) instead of get_unused_fd()

Macro get_unused_fd() is used to allocate a file descriptor with
default flags. Those default flags (0) can be "unsafe":
O_CLOEXEC must be used by default to not leak file descriptor
across exec().

Instead of macro get_unused_fd(), functions anon_inode_getfd()
or get_unused_fd_flags() should be used with flags given by userspace.
If not possible, flags should be set to O_CLOEXEC to provide userspace
with a default safe behavor.

In a further patch, get_unused_fd() will be removed so that
new code start using anon_inode_getfd() or get_unused_fd_flags()
with correct flags.

This patch replaces calls to get_unused_fd() with call to
get_unused_fd_flags(O_CLOEXEC) following advice from Erik Gilling.

Signed-off-by: Yann Droneaud <[e-mail]>
Cc: Erik Gilling <[e-mail]>
Cc: Colin Cross <[e-mail]>
Link: http://lkml.kernel.org/r/CACSP8SjZcpcpEtQHzcGYhf-MP7QGo0XpN7-uN7rmD=vNtopG=[e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/android/sw_sync.c

···
 static long sw_sync_ioctl_create_fence(struct sw_sync_timeline *obj,
 				       unsigned long arg)
 {
-	int fd = get_unused_fd();
+	int fd = get_unused_fd_flags(O_CLOEXEC);
 	int err;
 	struct sync_pt *pt;
 	struct sync_fence *fence;