On Sun, Mar 29, 2009 at 01:53:43AM +0100, Oleg Nesterov wrote: > Can't find the patch which introduced check_unsafe_exec(), so > I am asking here. > > How it is supposed to work? > > Let's suppose we have two threads T1 and T2. T1 exits, and calls > exit_fs(). > > exit_fs: > > tsk->fs = NULL; > // WINDOW > put_fs_struct(fs); > > Now, if T2 does exec() and check_unsafe_exec() happens in the WINDOW > above, we set LSM_UNSAFE_SHARE. > > Or we can race with sub-thread doing clone(CLONE_FS|CLONE_THREAD), > the new thread is not visible in ->thread_group, buy copy_fs() > can already increment fs->count. Frankly, I don't think we really care. Note that having several sub-threads and doing execve() in one of them will kill the rest, so you really want to do some kind of synchronization to get something similar to reasonable behaviour anyway. > Another question. Why do we check sighand->count? We always unshare > ->sighand on exec, see de_thread(). Correct. That check can and should go. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
