From nobody Mon Apr 13 14:28:51 2026 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 B15AFC4332F for ; Mon, 14 Nov 2022 02:33:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235614AbiKNCdC (ORCPT ); Sun, 13 Nov 2022 21:33:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229720AbiKNCdA (ORCPT ); Sun, 13 Nov 2022 21:33:00 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 53ACBDE94 for ; Sun, 13 Nov 2022 18:32:56 -0800 (PST) Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4N9YHp35T5zRp2l; Mon, 14 Nov 2022 10:32:38 +0800 (CST) Received: from kwepemm600003.china.huawei.com (7.193.23.202) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 14 Nov 2022 10:32:54 +0800 Received: from ubuntu1804.huawei.com (10.67.174.61) by kwepemm600003.china.huawei.com (7.193.23.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 14 Nov 2022 10:32:54 +0800 From: Yang Jihong To: , , CC: Subject: [PATCH] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line Date: Mon, 14 Nov 2022 10:29:46 +0800 Message-ID: <20221114022946.66255-1-yangjihong1@huawei.com> X-Mailer: git-send-email 2.30.GIT MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.67.174.61] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemm600003.china.huawei.com (7.193.23.202) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" print_trace_line may overflow seq_file buffer. If the event is not consumed, the while loop keeps peeking this event, causing a infinite loop. Signed-off-by: Yang Jihong --- kernel/trace/trace.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 47a44b055a1d..2a8d5c68c29b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6788,6 +6788,19 @@ tracing_read_pipe(struct file *filp, char __user *ub= uf, if (ret =3D=3D TRACE_TYPE_PARTIAL_LINE) { /* don't print partial lines */ iter->seq.seq.len =3D save_len; + + /* + * If one trace_line of the tracer overflows seq_file + * buffer, trace_seq_to_user returns -EBUSY because + * nothing in the sequence (iter->seq.seq.len =3D \ + * iter->seq.seq.readpos =3D 0). + * In this case, we need to consume, otherwise, + * "while" will peek this event next time, resulting + * in an infinite loop. + */ + if (trace_seq_has_overflowed(&iter->seq)) + trace_consume(iter); + break; } if (ret !=3D TRACE_TYPE_NO_CONSUME) --=20 2.30.GIT