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 D0F66C43217 for ; Thu, 24 Nov 2022 13:02:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230052AbiKXNCZ (ORCPT ); Thu, 24 Nov 2022 08:02:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230218AbiKXNCB (ORCPT ); Thu, 24 Nov 2022 08:02:01 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 794058754A for ; Thu, 24 Nov 2022 05:02:00 -0800 (PST) Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4NHymc5ScCzHw3R; Thu, 24 Nov 2022 21:01:20 +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; Thu, 24 Nov 2022 21:01:52 +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; Thu, 24 Nov 2022 21:01:52 +0800 From: Yang Jihong To: , , CC: Subject: [PATCH v3] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line Date: Thu, 24 Nov 2022 20:58:50 +0800 Message-ID: <20221124125850.155449-1-yangjihong1@huawei.com> X-Mailer: git-send-email 2.30.GIT MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII 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 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 | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a7fe0e115272..55733224fa88 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6787,7 +6787,27 @@ 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 it, otherwise, + * while loop will peek this event next time, + * resulting in an infinite loop. + */ + if (trace_seq_has_overflowed(&iter->seq)) { + /* + * Here we only consider the case that one + * print_trace_line() fills the entire trace_seq + * in one shot, in that case, iter->seq.seq.len is zero, + * we simply output a log of too long line to inform the user. + */ + iter->seq.full = 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 = save_len; break; } -- 2.30.GIT