From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751860AbdBOPKn (ORCPT ); Wed, 15 Feb 2017 10:10:43 -0500 Received: from mail.kernel.org ([198.145.29.136]:37838 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751356AbdBOPKm (ORCPT ); Wed, 15 Feb 2017 10:10:42 -0500 Date: Thu, 16 Feb 2017 00:10:30 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Peter Zijlstra , Ananth N Mavinakayanahalli , Thomas Gleixner , "H . Peter Anvin" , Namhyung Kim , Andrew Morton Subject: Re: [PATCH V2 1/2] tracing/probes: Fix a warning message to show correct maximum length Message-Id: <20170216001030.bd1ee215ea9d31289e2441ed@kernel.org> In-Reply-To: <20170210110434.36d50ed2@gandalf.local.home> References: <20170210075302.GB24405@gmail.com> <148673290462.2579.7966778294009665632.stgit@devbox> <20170210110434.36d50ed2@gandalf.local.home> X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.30; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 10 Feb 2017 11:04:34 -0500 Steven Rostedt wrote: > On Fri, 10 Feb 2017 22:21:55 +0900 > Masami Hiramatsu wrote: > > > Since tracing/*probe_events will accept a probe definition > > up to 4096 - 2 ('\n' and '\0') bytes, it must show 4094 instead > > of 4096 in warning message. > > Actually, during the testing I found that we don't need the '\n'. > > echo -n 'p:irq do_IRQ a=@jiffies_64' > kprobe_events > > works just fine. My tests work with 4095 characters. Before and after > my patch. Yeah, I see. I concider the case that if the writer writes 4095 chars command + '\n' + next command, it will fail, that is what I pointed out below note. > > > > Note that there is one possible case of exceed 4094. If user > > prepare 4096 bytes null-terminated string and syscall write > > it with the count == 4095, then it can be accepted. However, > > if user puts a '\n' after that, it must rejected. > > So IMHO, the warning message should indicate shorter one, > > since it is safer. Thank you, > > > > Signed-off-by: Masami Hiramatsu > > --- > > kernel/trace/trace_probe.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > > index 2a06f1f..847c1e0 100644 > > --- a/kernel/trace/trace_probe.c > > +++ b/kernel/trace/trace_probe.c > > @@ -678,8 +678,9 @@ ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer, > > if (done + size < count) { > > if (buf != kbuf) > > break; > > + /* This can accept WRITE_BUFSIZE - 2 ('\n' + '\0') */ > > pr_warn("Line length is too long: Should be less than %d\n", > > - WRITE_BUFSIZE); > > + WRITE_BUFSIZE - 2); > > ret = -EINVAL; > > goto out; > > } > -- Masami Hiramatsu