tracing-Do-not-allow-llseek-to-set_ftrace_filter.patch

From b74e20102c13e1aa0e4470d7301ecab7192956c1 Mon Sep 17 00:00:00 2001
From: Steven Rostedt <srostedt@redhat.com>
Date: Wed, 8 Sep 2010 11:20:37 -0400
Subject: [PATCH] tracing: Do not allow llseek to set_ftrace_filter

commit dc7dde7adbc57b7461b4b1302c94fe31699f60e2 in tip.

Reading the file set_ftrace_filter does three things.

1) shows whether or not filters are set for the function tracer
2) shows what functions are set for the function tracer
3) shows what triggers are set on any functions

3 is independent from 1 and 2.

The way this file currently works is that it is a state machine,
and as you read it, it may change state. But this assumption breaks
when you use lseek() on the file. The state machine gets out of sync
and the t_show() may use the wrong pointer and cause a kernel oops.

Luckily, this will only kill the app that does the lseek, but the app
dies while holding a mutex. This prevents anyone else from using the
set_ftrace_filter file (or any other function tracing file for that matter).

A real fix for this is to rewrite the code, but that is too much for
a -rc release or stable. This patch simply disables llseek on the
set_ftrace_filter() file for now, and we can do the proper fix for the
next major release.

Reported-by: Robert Swiecki <swiecki@google.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Tavis Ormandy <taviso@google.com>
Cc: Eugene Teo <eugene@redhat.com>
Cc: vendor-sec@lst.de
Cc: <stable@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a6d0ebe..4a23d1f 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2410,7 +2410,7 @@ static const struct file_operations ftrace_filter_fops = {
 	.open = ftrace_filter_open,
 	.read = seq_read,
 	.write = ftrace_filter_write,
-	.llseek = ftrace_regex_lseek,
+	.llseek = no_llseek,
 	.release = ftrace_filter_release,
 };
 
-- 
1.7.1.1