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[2620:137:e000::1:20]) by mx.google.com with ESMTP id g10-20020a170902d1ca00b00186994f6e90si3000215plb.529.2022.11.18.02.41.05; Fri, 18 Nov 2022 02:41:18 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241645AbiKRK2c (ORCPT + 99 others); Fri, 18 Nov 2022 05:28:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235171AbiKRK23 (ORCPT ); Fri, 18 Nov 2022 05:28:29 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D7768DF09 for ; Fri, 18 Nov 2022 02:28:28 -0800 (PST) Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4NDCfL5h3xzHvrW; Fri, 18 Nov 2022 18:27:54 +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; Fri, 18 Nov 2022 18:28:27 +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; Fri, 18 Nov 2022 18:28:26 +0800 From: Yang Jihong To: , , CC: Subject: [PATCH v2] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line Date: Fri, 18 Nov 2022 18:25:21 +0800 Message-ID: <20221118102521.62362-1-yangjihong1@huawei.com> X-Mailer: git-send-email 2.30.GIT MIME-Version: 1.0 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 X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1749438423005651943?= X-GMAIL-MSGID: =?utf-8?q?1749830157004474499?= 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 --- Changes since v1: - Print partial line to show the broken trace event when overflowed print_trace_line kernel/trace/trace.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 47a44b055a1d..81c36dc80212 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6786,7 +6786,32 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, ret = print_trace_line(iter); if (ret == TRACE_TYPE_PARTIAL_LINE) { - /* don't print partial lines */ + /* + * If one trace_line of the tracer overflows seq_file + * buffer, trace_seq_to_user returns -EBUSY. + * In this case, we need to consume, otherwise, + * while loop will peek this event next time, + * resulting in an infinite loop. + */ + if (trace_seq_has_overflowed(&iter->seq)) { + /* + * Print the partial line, + * that way we can see the broken trace event. + */ + char dots[] = "...\n"; + + iter->seq.full = 0; + if (seq_buf_buffer_left(&iter->seq.seq) < strlen(dots)) { + iter->seq.seq.len = + seq_buf_used(&iter->seq.seq) - strlen(dots); + } + trace_seq_puts(&iter->seq, dots); + + trace_consume(iter); + break; + } + + /* In other cases, don't print partial lines */ iter->seq.seq.len = save_len; break; }