From nobody Tue Dec 30 16:38:23 2025 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 B8EA4C4167D for ; Tue, 14 Nov 2023 16:33:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233724AbjKNQdz (ORCPT ); Tue, 14 Nov 2023 11:33:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233721AbjKNQdw (ORCPT ); Tue, 14 Nov 2023 11:33:52 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B48AD182 for ; Tue, 14 Nov 2023 08:33:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1699979629; 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=2Mg3UCFMr1SH7PUf+Sl5YMeVrQDgFkP/RxqlBy+YY5Y=; b=KMLxl460hnji69qZ7WIoNEWpWS44Ei8hH6CpZZIXFIFrsOWvyAPmp4FiJqmqZV1c39vd4z iYkgXySYtQlgacst/95ZWpbJTcIHrFLUEWr4kiWeQOSO8zp/JQQbtTwiYGf2b/C4u0mHPN mfs2WeyZFheM3mzTjEkHT2rGLyvcO+8= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-140-areqUpPuN-OXmCaWVP_OIg-1; Tue, 14 Nov 2023 11:33:45 -0500 X-MC-Unique: areqUpPuN-OXmCaWVP_OIg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 24813811E93; Tue, 14 Nov 2023 16:33:44 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.253]) by smtp.corp.redhat.com (Postfix) with SMTP id 46294493113; Tue, 14 Nov 2023 16:33:42 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 14 Nov 2023 17:32:39 +0100 (CET) Date: Tue, 14 Nov 2023 17:32:37 +0100 From: Oleg Nesterov To: Alexei Starovoitov , Yonghong Song Cc: Chuyi Zhou , Daniel Borkmann , Kui-Feng Lee , linux-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: [PATCH 2/3] bpf: bpf_iter_task_next: use __next_thread() rather than next_thread() Message-ID: <20231114163237.GA897@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20231114163211.GA874@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 =3D=3D 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 Acked-by: Yonghong Song --- kernel/bpf/task_iter.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 51ae15e2b290..d42e08d0d0b7 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -1015,12 +1015,11 @@ __bpf_kfunc struct task_struct *bpf_iter_task_next(= struct bpf_iter_task *it) if (flags =3D=3D BPF_TASK_ITER_ALL_PROCS) goto get_next_task; =20 - kit->pos =3D next_thread(kit->pos); - if (kit->pos =3D=3D kit->task) { - if (flags =3D=3D BPF_TASK_ITER_PROC_THREADS) { - kit->pos =3D NULL; + kit->pos =3D __next_thread(kit->pos); + if (!kit->pos) { + if (flags =3D=3D BPF_TASK_ITER_PROC_THREADS) return pos; - } + kit->pos =3D kit->task; } else return pos; =20 --=20 2.25.1.362.g51ebf55