> On Thu, Dec 05, 2019 at 11:44:53PM +0000, Sargun Dhillon wrote: > > > +static int ptrace_getfd(struct task_struct *child, unsigned long fd) > > +{ > > + struct files_struct *files; > > + struct file *file; > > + int ret = 0; > > + > > + files = get_files_struct(child); > > + if (!files) > > + return -ENOENT; > > + > > + spin_lock(&files->file_lock); > > + file = fcheck_files(files, fd); > > + if (!file) > > + ret = -EBADF; > > + else > > + get_file(file); > > + spin_unlock(&files->file_lock); > > + put_files_struct(files); may be someone can finally create a helper for this, it can have more users. say, struct file *get_task_file(task, fd) { struct file *file = NULL; task_lock(task); rcu_read_lock(); if (task->files) { file = fcheck_files(task->files, fd); if (file) get_file(file); } rcu_read_unlock(); task_unlock(task); return file; } no need to get/put files_struct, no need to take ->file_lock. > > + > > + if (ret) > > + goto out; > > + > > + ret = get_unused_fd_flags(0); > > + if (ret >= 0) > > + fd_install(ret, file); > > + > > + fput(file); this looks wrong or I am totally confused... if (ret >= 0) fd_install(file); else fput(file); ? > > @@ -1265,7 +1299,8 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr, > > } > > > > ret = ptrace_check_attach(child, request == PTRACE_KILL || > > - request == PTRACE_INTERRUPT); > > + request == PTRACE_INTERRUPT || > > + request == PTRACE_GETFD); Hmm. not sure why do you want this... But OK, we do not need to stop the tracee. Oleg.