From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752113Ab0HMUzM (ORCPT ); Fri, 13 Aug 2010 16:55:12 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.125]:64177 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751599Ab0HMUzK (ORCPT ); Fri, 13 Aug 2010 16:55:10 -0400 X-Authority-Analysis: v=1.1 cv=lkxCD/5/46GCnpIirYorSQYl6SFYRu3AvdhUIdWuqHk= c=1 sm=0 a=oC6nfymtsbUA:10 a=Q9fys5e9bTEA:10 a=IXo+6rlC6z1XzBFn1RNpIA==:17 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=20KFwNOVAAAA:8 a=meVymXHHAAAA:8 a=MXK2Ef5vOhNAgs8QZVMA:9 a=AVB56uzOcn3CwX2NMaEA:7 a=QjhhHKUI10q-9ZOTEKU4w9Foo08A:4 a=PUjeQqilurYA:10 a=MSl-tDqOz04A:10 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=IXo+6rlC6z1XzBFn1RNpIA==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.87.39 Subject: [PATCH][GIT PULL] tracing: Sanitize value returned from write(trace_marker, "...", len) From: Steven Rostedt To: LKML Cc: Ingo Molnar , Frederic Weisbecker , Marcin Slusarz Content-Type: text/plain; charset="ISO-8859-15" Date: Fri, 13 Aug 2010 16:55:07 -0400 Message-ID: <1281732907.3058.77.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.30.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo, I had this sitting in my quilt queue, and did not realize I never committed it. This is on top of my previous two pull requests. Thanks, -- Steve Please pull the latest tip/perf/urgent-3 tree, which can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git tip/perf/urgent-3 Marcin Slusarz (1): tracing: Sanitize value returned from write(trace_marker, "...", len) ---- kernel/trace/trace.c | 11 ++++++++--- 1 files changed, 8 insertions(+), 3 deletions(-) --------------------------- commit 1aa54bca6ee0d07ebcafb8ca8074b624d80724aa Author: Marcin Slusarz Date: Wed Jul 28 01:18:01 2010 +0200 tracing: Sanitize value returned from write(trace_marker, "...", len) When userspace code writes non-new-line-terminated string to trace_marker file, write handler appends new-line and returns number of bytes written to trace buffer, so write(fd, "abc", 3) will return 4 That's unexpected and unfortunately it confuses glibc's fprintf function. Example: int main() { fprintf(stderr, "abc"); return 0; } $ gcc test.c -o test $ echo mmiotrace > /sys/kernel/debug/tracing/current_tracer $ ./test 2>/sys/kernel/debug/tracing/trace_marker results in infinite loop: write(fd, "abc", 3) = 4 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 (...) ...and kernel trace buffer full of empty markers. Fix it by sanitizing write return value. Signed-off-by: Marcin Slusarz LKML-Reference: <20100727231801.GB2826@joi.lan> Cc: Frederic Weisbecker Cc: Ingo Molnar Signed-off-by: Steven Rostedt diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 086d363..88b42d1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3498,6 +3498,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *fpos) { char *buf; + size_t written; if (tracing_disabled) return -EINVAL; @@ -3519,11 +3520,15 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, } else buf[cnt] = '\0'; - cnt = mark_printk("%s", buf); + written = mark_printk("%s", buf); kfree(buf); - *fpos += cnt; + *fpos += written; - return cnt; + /* don't tell userspace we wrote more - it might confuse them */ + if (written > cnt) + written = cnt; + + return written; } static int tracing_clock_show(struct seq_file *m, void *v)