Hello Christian Brauner,
The patch d089d9d056c0: "file: convert to SLAB_TYPESAFE_BY_RCU" from
Sep 29, 2023 (linux-next), leads to the following Smatch static
checker warning:
kernel/bpf/task_iter.c:302 task_file_seq_get_next()
warn: ignoring unreachable code.
kernel/bpf/task_iter.c
258 static struct file *
259 task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info)
260 {
261 u32 saved_tid = info->tid;
262 struct task_struct *curr_task;
263 unsigned int curr_fd = info->fd;
264
265 /* If this function returns a non-NULL file object,
266 * it held a reference to the task/file.
267 * Otherwise, it does not hold any reference.
268 */
269 again:
270 if (info->task) {
271 curr_task = info->task;
272 curr_fd = info->fd;
273 } else {
274 curr_task = task_seq_get_next(&info->common, &info->tid, true);
275 if (!curr_task) {
276 info->task = NULL;
277 return NULL;
278 }
279
280 /* set info->task */
281 info->task = curr_task;
282 if (saved_tid == info->tid)
283 curr_fd = info->fd;
284 else
285 curr_fd = 0;
286 }
287
288 rcu_read_lock();
289 for (;; curr_fd++) {
290 struct file *f;
291 f = task_lookup_next_fdget_rcu(curr_task, &curr_fd);
292 if (!f)
293 continue;
Should this be a break?
294
295 /* set info->fd */
296 info->fd = curr_fd;
297 rcu_read_unlock();
298 return f;
299 }
300
301 /* the current task is done, go to the next task */
--> 302 rcu_read_unlock();
Unreachable
303 put_task_struct(curr_task);
304
305 if (info->common.type == BPF_TASK_ITER_TID) {
306 info->task = NULL;
307 return NULL;
308 }
309
310 info->task = NULL;
311 info->fd = 0;
312 saved_tid = ++(info->tid);
313 goto again;
314 }
regards,
dan carpenter
