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bpf: task_group_seq_get_next: cleanup the usage of next_thread()

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1. find_pid_ns() + get_pid_task() under rcu_read_lock() guarantees that we
   can safely iterate the task->thread_group list. Even if this task exits
   right after get_pid_task() (or goto retry) and pid_alive() returns 0.

   Kill the unnecessary pid_alive() check.

2. next_thread() simply can't return NULL, kill the bogus "if (!next_task)"
   check.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230905154646.GA24928@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Oleg Nesterov 2023-09-05 17:46:46 +02:00 committed by Alexei Starovoitov
parent 35897c3c52
commit 1a00ef57d9
1 changed files with 0 additions and 7 deletions
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7
kernel/bpf/task_iter.c
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@ -75,15 +75,8 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm
return NULL;
retry:
if (!pid_alive(task)) {
put_task_struct(task);
return NULL;
}
next_task = next_thread(task);
put_task_struct(task);
if (!next_task)
return NULL;
saved_tid = *tid;
*tid = __task_pid_nr_ns(next_task, PIDTYPE_PID, common->ns);