From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757677AbeAIWyi (ORCPT + 1 other); Tue, 9 Jan 2018 17:54:38 -0500 Received: from mail.kernel.org ([198.145.29.99]:42386 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752684AbeAIWyh (ORCPT ); Tue, 9 Jan 2018 17:54:37 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7A0B720693 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Tue, 9 Jan 2018 17:54:34 -0500 From: Steven Rostedt To: changbin.du@intel.com Cc: jolsa@redhat.com, peterz@infradead.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH 1/3] tracing: detect the string termination character when parsing user input string Message-ID: <20180109175434.77163e52@vmware.local.home> In-Reply-To: <1515491748-25926-2-git-send-email-changbin.du@intel.com> References: <1515491748-25926-1-git-send-email-changbin.du@intel.com> <1515491748-25926-2-git-send-email-changbin.du@intel.com> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.31; 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 Return-Path: On Tue, 9 Jan 2018 17:55:46 +0800 changbin.du@intel.com wrote: > From: Changbin Du > > The usersapce can give a '\0' terminated C string or even has '\0' at the > middle of input buffer. We need handle both these two cases correctly. What do you define as correctly. Because I'm not seeing it. > > Before this change, trace_get_user() will return a parsed string "\0" in > below case. It is not expected (expects it skip all inputs) and cause the > caller failed. > > open("/sys/kernel/debug/tracing//set_ftrace_pid", O_WRONLY|O_TRUNC) = 3 > write(3, " \0", 2) = -1 EINVAL (Invalid argument) That looks more like a feature and not a bug. > > This patch try to make the parser '\0' aware to fix such issue. Why? > > Since the caller expects trace_get_user() to parse whole input buffer, so > this patch treat '\0' as a separator as whitespace. It looks more like we are trying to fix a userspace bug via the kernel. I'm not liking this. So NACK. -- Steve > > Signed-off-by: Changbin Du > --- > kernel/trace/trace.c | 17 +++++++++++------ > 1 file changed, 11 insertions(+), 6 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 2a8d8a2..18526a1 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -1194,9 +1194,14 @@ void trace_parser_put(struct trace_parser *parser) > parser->buffer = NULL; > } > > +static inline bool is_space_or_zero(char ch) > +{ > + return isspace(ch) || !ch; > +} > + > /* > - * trace_get_user - reads the user input string separated by space > - * (matched by isspace(ch)) > + * trace_get_user - reads the user input string separated by space or '\0' > + * (matched by is_space_or_zero(ch)) > * > * For each string found the 'struct trace_parser' is updated, > * and the function returns. > @@ -1228,7 +1233,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > */ > if (!parser->cont) { > /* skip white space */ > - while (cnt && isspace(ch)) { > + while (cnt && is_space_or_zero(ch)) { > ret = get_user(ch, ubuf++); > if (ret) > goto out; > @@ -1237,7 +1242,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* only spaces were written */ > - if (isspace(ch)) { > + if (is_space_or_zero(ch)) { > *ppos += read; > ret = read; > goto out; > @@ -1247,7 +1252,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* read the non-space input */ > - while (cnt && !isspace(ch)) { > + while (cnt && !is_space_or_zero(ch)) { > if (parser->idx < parser->size - 1) > parser->buffer[parser->idx++] = ch; > else { > @@ -1262,7 +1267,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, > } > > /* We either got finished input or we have to wait for another call. */ > - if (isspace(ch)) { > + if (is_space_or_zero(ch)) { > parser->buffer[parser->idx] = 0; > parser->cont = false; > } else if (parser->idx < parser->size - 1) {