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Message-ID: <20230825161939.GA16859@redhat.com>
Date: Fri, 25 Aug 2023 18:19:39 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Yonghong Song <yhs@...com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Daniel Borkmann <daniel@...earbox.net>,
Kui-Feng Lee <kuifeng@...com>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...nel.org>,
bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/6] bpf: task_group_seq_get_next: cleanup the usage of
next_thread()
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@...hat.com>
---
kernel/bpf/task_iter.c | 7 -------
1 file changed, 7 deletions(-)
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index c4ab9d6cdbe9..4d1125108014 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -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);
--
2.25.1.362.g51ebf55
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