From nobody Fri Sep 19 03:48:22 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 24BDAC4321E for ; Tue, 29 Nov 2022 11:33:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231842AbiK2Ldn (ORCPT ); Tue, 29 Nov 2022 06:33:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233140AbiK2LdV (ORCPT ); Tue, 29 Nov 2022 06:33:21 -0500 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEB17D95 for ; Tue, 29 Nov 2022 03:33:09 -0800 (PST) Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.57]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4NM0Vd6S4GzJnyB; Tue, 29 Nov 2022 19:29:45 +0800 (CST) Received: from kwepemm600003.china.huawei.com (7.193.23.202) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Tue, 29 Nov 2022 19:33:08 +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; Tue, 29 Nov 2022 19:33:07 +0800 From: Yang Jihong To: , , CC: Subject: [PATCH v4] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line Date: Tue, 29 Nov 2022 19:30:09 +0800 Message-ID: <20221129113009.182425-1-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: dggems703-chm.china.huawei.com (10.3.19.180) 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 | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a7fe0e115272..de7c99f4b539 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6787,7 +6787,20 @@ tracing_read_pipe(struct file *filp, char __user *ub= uf, =20 ret =3D print_trace_line(iter); if (ret =3D=3D TRACE_TYPE_PARTIAL_LINE) { - /* don't print partial lines */ + /* + * If one print_trace_line() fills entire trace_seq in one shot, + * trace_seq_to_user() will returns -EBUSY because save_len =3D=3D 0, + * In this case, we need to consume it, otherwise, loop will peek + * this event next time, resulting in an infinite loop. + */ + if (save_len =3D=3D 0) { + iter->seq.full =3D 0; + trace_seq_puts(&iter->seq, "[LINE TOO BIG]\n"); + trace_consume(iter); + break; + } + + /* In other cases, don't print partial lines */ iter->seq.seq.len =3D save_len; break; } --=20 2.30.GIT