Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754135AbeAOLvV (ORCPT + 1 other); Mon, 15 Jan 2018 06:51:21 -0500 Received: from mga11.intel.com ([192.55.52.93]:44290 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932900AbeAOLu3 (ORCPT ); Mon, 15 Jan 2018 06:50:29 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,363,1511856000"; d="scan'208";a="195597396" From: changbin.du@intel.com To: rostedt@goodmis.org 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, Changbin Du Subject: [PATCH v2 1/3] tracing: detect the string termination character when parsing user input string Date: Mon, 15 Jan 2018 19:41:12 +0800 Message-Id: <1516016474-5581-2-git-send-email-changbin.du@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1516016474-5581-1-git-send-email-changbin.du@intel.com> References: <1516016474-5581-1-git-send-email-changbin.du@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Changbin Du The usersapce can give a '\0' terminated C string in the input buffer. Before this change, trace_get_user() will return a parsed string "\0" in below case which 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) while parse can handle spaces, so below works. $ echo "" > set_ftrace_pid $ echo " " > set_ftrace_pid $ echo -n " " > set_ftrace_pid This patch try to make the parser '\0' aware to fix such issue. When parser sees a '\0' it stops further parsing. With this change, write(3, " \0", 2) will work. Signed-off-by: Changbin Du --- v2: Stop parsing when '\0' found. --- kernel/trace/trace.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 2a8d8a2..144d08e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1237,7 +1237,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, } /* only spaces were written */ - if (isspace(ch)) { + if (isspace(ch) || !ch) { *ppos += read; ret = read; goto out; @@ -1247,7 +1247,7 @@ int trace_get_user(struct trace_parser *parser, const char __user *ubuf, } /* read the non-space input */ - while (cnt && !isspace(ch)) { + while (cnt && !isspace(ch) && ch) { if (parser->idx < parser->size - 1) parser->buffer[parser->idx++] = ch; else { @@ -1262,7 +1262,7 @@ 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 (isspace(ch) || !ch) { parser->buffer[parser->idx] = 0; parser->cont = false; } else if (parser->idx < parser->size - 1) { -- 2.7.4