From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4ED1C71134 for ; Fri, 25 Aug 2023 16:22:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343962AbjHYQVw (ORCPT ); Fri, 25 Aug 2023 12:21:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343951AbjHYQVX (ORCPT ); Fri, 25 Aug 2023 12:21:23 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54A3719A0 for ; Fri, 25 Aug 2023 09:20:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692980435; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to; bh=9YOqEsz0E9i9rWLFPxwqu5HEnoteHVcXSEYvs1ICBUo=; b=eYFGOgLcjmO5F/h71dm1jVdu2owLsYhltDlSrFSH43HjeVtVwpZk+HqIxM8s1MJP3v7rm2 uxGZ8Iyub8eInDHuYBMoNDbnenk6Gu2ToWp+wDEl+gqvrVdZm4QSi09x2P1c/Yd3Ga9Thl 18esP0FIp06jm9YlG0QT7x7/18U0Krk= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-553-AHXAlR9qNJG_uPLbCjlKdQ-1; Fri, 25 Aug 2023 12:20:30 -0400 X-MC-Unique: AHXAlR9qNJG_uPLbCjlKdQ-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 842BA185A78B; Fri, 25 Aug 2023 16:20:29 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.136]) by smtp.corp.redhat.com (Postfix) with SMTP id 10352492C14; Fri, 25 Aug 2023 16:20:26 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 25 Aug 2023 18:19:43 +0200 (CEST) Date: Fri, 25 Aug 2023 18:19:39 +0200 From: Oleg Nesterov To: Andrew Morton , Yonghong Song Cc: "Eric W. Biederman" , Linus Torvalds , Daniel Borkmann , Kui-Feng Lee , Andrii Nakryiko , Martin KaFai Lau , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/6] bpf: task_group_seq_get_next: cleanup the usage of next_thread() Message-ID: <20230825161939.GA16859@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230825161842.GA16750@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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