Messages in this thread Patch in this message | | | Date | Tue, 14 Nov 2023 17:32:34 +0100 | From | Oleg Nesterov <> | Subject | [PATCH 1/3] bpf: task_group_seq_get_next: use __next_thread() rather than next_thread() |
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Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c is the last user and the usage is wrong.
task_group_seq_get_next() can return the group leader twice if it races with mt-thread exec which changes the group->leader's pid.
Change the main loop to use __next_thread(), kill "next_tid == common->pid" check.
__next_thread() can't loop forever, we can also change this code to retry if next_tid == 0.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/bpf/task_iter.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 26082b97894d..51ae15e2b290 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -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; -- 2.25.1.362.g51ebf55
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