Commit 5a34f9da authored Nov 14, 2023 by Oleg Nesterov Committed by Alexei Starovoitov Nov 19, 2023

bpf: bpf_iter_task_next: use __next_thread() rather than next_thread()



Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c
is the last user and the usage is wrong.

bpf_iter_task_next() can loop forever, "kit->pos == kit->task" can never
happen if kit->pos execs. Change this code to use __next_thread().

With or without this change the usage of kit->pos/task and next_task()
doesn't look nice, see the next patch.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20231114163237.GA897@redhat.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>

parent 2d161805

kernel/bpf/task_iter.c

+4 −5

Original line number	Diff line number	Diff line
		@@ -1015,12 +1015,11 @@ __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;
		kit->pos = __next_thread(kit->pos);
		if (!kit->pos) {
		if (flags == BPF_TASK_ITER_PROC_THREADS)
		return pos;
		}
		kit->pos = kit->task;
		} else
		return pos;