From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751540AbcFXCOO (ORCPT ); Thu, 23 Jun 2016 22:14:14 -0400 Received: from mga09.intel.com ([134.134.136.24]:39529 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750847AbcFXCOM convert rfc822-to-8bit (ORCPT ); Thu, 23 Jun 2016 22:14:12 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,518,1459839600"; d="scan'208";a="834255814" From: "Xing, Zhengjun" To: Steven Rostedt , "linux-kernel@vger.kernel.org" CC: Linus Torvalds , Ingo Molnar , Andrew Morton , Namhyung Kim , "stable@vger.kernel.org" Subject: RE: [PATCH 1/2] tracing: Handle NULL formats in hold_module_trace_bprintk_format() Thread-Topic: [PATCH 1/2] tracing: Handle NULL formats in hold_module_trace_bprintk_format() Thread-Index: AQHRyvs8+Fr1g3ZvJU6GpEQXUSUt6Z/349BQ Date: Fri, 24 Jun 2016 02:14:06 +0000 Message-ID: <13D79DBE8302154F8AC69AD78FCDF45936BAABDE@SHSMSX101.ccr.corp.intel.com> References: <20160620135253.069384486@goodmis.org> <20160620135356.253802298@goodmis.org> In-Reply-To: <20160620135356.253802298@goodmis.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ctpclassification: CTP_IC x-titus-metadata-40: eyJDYXRlZ29yeUxhYmVscyI6IiIsIk1ldGFkYXRhIjp7Im5zIjoiaHR0cDpcL1wvd3d3LnRpdHVzLmNvbVwvbnNcL0ludGVsMyIsImlkIjoiNWI2ZWIwZTEtMTI2Mi00Njg5LWIzNDUtY2NmNmNjOGM1NjI1IiwicHJvcHMiOlt7Im4iOiJDVFBDbGFzc2lmaWNhdGlvbiIsInZhbHMiOlt7InZhbHVlIjoiQ1RQX0lDIn1dfV19LCJTdWJqZWN0TGFiZWxzIjpbXSwiVE1DVmVyc2lvbiI6IjE1LjkuNi42IiwiVHJ1c3RlZExhYmVsSGFzaCI6Im9XQlpuTE83WU0wZElWa1EzM1BRSFRaTStCRjZPN1plMUNkMVVsM3VRZms9In0= x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I agree with you. You can also add me to the "Signed-off-by". Best Regards, Zhengjun -----Original Message----- From: Steven Rostedt [mailto:rostedt@goodmis.org] Sent: Monday, June 20, 2016 9:53 PM To: linux-kernel@vger.kernel.org Cc: Linus Torvalds ; Ingo Molnar ; Andrew Morton ; Xing, Zhengjun ; Namhyung Kim ; stable@vger.kernel.org Subject: [PATCH 1/2] tracing: Handle NULL formats in hold_module_trace_bprintk_format() From: "Steven Rostedt (Red Hat)" If a task uses a non constant string for the format parameter in trace_printk(), then the trace_printk_fmt variable is set to NULL. This variable is then saved in the __trace_printk_fmt section. The function hold_module_trace_bprintk_format() checks to see if duplicate formats are used by modules, and reuses them if so (saves them to the list if it is new). But this function calls lookup_format() that does a strcmp() to the value (which is now NULL) and can cause a kernel oops. This wasn't an issue till 3debb0a9ddb ("tracing: Fix trace_printk() to print when not using bprintk()") which added "__used" to the trace_printk_fmt variable, and before that, the kernel simply optimized it out (no NULL value was saved). The fix is simply to handle the NULL pointer in lookup_format() and have the caller ignore the value if it was NULL. Link: http://lkml.kernel.org/r/1464769870-18344-1-git-send-email-zhengjun.xing@intel.com Reported-by: xingzhen Acked-by: Namhyung Kim Fixes: 3debb0a9ddb ("tracing: Fix trace_printk() to print when not using bprintk()") Cc: stable@vger.kernel.org # v3.5+ Signed-off-by: Steven Rostedt --- kernel/trace/trace_printk.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c index f96f0383f6c6..ad1d6164e946 100644 --- a/kernel/trace/trace_printk.c +++ b/kernel/trace/trace_printk.c @@ -36,6 +36,10 @@ struct trace_bprintk_fmt { static inline struct trace_bprintk_fmt *lookup_format(const char *fmt) { struct trace_bprintk_fmt *pos; + + if (!fmt) + return ERR_PTR(-EINVAL); + list_for_each_entry(pos, &trace_bprintk_fmt_list, list) { if (!strcmp(pos->fmt, fmt)) return pos; @@ -57,7 +61,8 @@ void hold_module_trace_bprintk_format(const char **start, const char **end) for (iter = start; iter < end; iter++) { struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter); if (tb_fmt) { - *iter = tb_fmt->fmt; + if (!IS_ERR(tb_fmt)) + *iter = tb_fmt->fmt; continue; } -- 2.8.0.rc3