Commit 3e124aa6 authored by Alexei Starovoitov's avatar Alexei Starovoitov
Browse files

Merge branch 'bpf-kernel-bpf-task_iter-c-don-t-abuse-next_thread' 

Oleg Nesterov says:

====================
bpf: kernel/bpf/task_iter.c: don't abuse next_thread()

Compile tested.

Every lockless usage of next_thread() was wrong, bpf/task_iter.c is
the last user and is no exception.

====================

Link: https://lore.kernel.org/r/20231114163211.GA874@redhat.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parents 16b3129e ac8148d9

kernel/bpf/task_iter.c

+11 −18
Original line number Diff line number Diff line
@@ -70,15 +70,13 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm 
		return NULL;



retry:

	task = next_thread(task);

	task = __next_thread(task);

	if (!task)

		return NULL;



	next_tid = __task_pid_nr_ns(task, PIDTYPE_PID, common->ns);

	if (!next_tid || next_tid == common->pid) {

		/* Run out of tasks of a process.  The tasks of a

		 * thread_group are linked as circular linked list.

		 */

		return NULL;

	}

	if (!next_tid)

		goto retry;



	if (skip_if_dup_files && task->files == task->group_leader->files)

		goto retry;
@@ -980,7 +978,6 @@ __bpf_kfunc int bpf_iter_task_new(struct bpf_iter_task *it, 
	BUILD_BUG_ON(__alignof__(struct bpf_iter_task_kern) !=

					__alignof__(struct bpf_iter_task));



	kit->task = kit->pos = NULL;

	switch (flags) {

	case BPF_TASK_ITER_ALL_THREADS:

	case BPF_TASK_ITER_ALL_PROCS:
@@ -1017,20 +1014,16 @@ __bpf_kfunc struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it) 
	if (flags == BPF_TASK_ITER_ALL_PROCS)

		goto get_next_task;



	kit->pos = next_thread(kit->pos);

	if (kit->pos == kit->task) {

		if (flags == BPF_TASK_ITER_PROC_THREADS) {

			kit->pos = NULL;

			return pos;

		}

	} else

	kit->pos = __next_thread(kit->pos);

	if (kit->pos || flags == BPF_TASK_ITER_PROC_THREADS)

		return pos;



get_next_task:

	kit->pos = next_task(kit->pos);

	kit->task = kit->pos;

	if (kit->pos == &init_task)

	kit->task = next_task(kit->task);

	if (kit->task == &init_task)

		kit->pos = NULL;

	else

		kit->pos = kit->task;



	return pos;

}