Patch "tracing/kprobes: Enforce kprobes teardown after testing" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    tracing/kprobes: Enforce kprobes teardown after testing

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tracing-kprobes-enforce-kprobes-teardown-after-testing.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 30e7d894c1478c88d50ce94ddcdbd7f9763d9cdd Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 17 May 2017 10:19:49 +0200
Subject: tracing/kprobes: Enforce kprobes teardown after testing

From: Thomas Gleixner <tglx@linutronix.de>

commit 30e7d894c1478c88d50ce94ddcdbd7f9763d9cdd upstream.

Enabling the tracer selftest triggers occasionally the warning in
text_poke(), which warns when the to be modified page is not marked
reserved.

The reason is that the tracer selftest installs kprobes on functions marked
__init for testing. These probes are removed after the tests, but that
removal schedules the delayed kprobes_optimizer work, which will do the
actual text poke. If the work is executed after the init text is freed,
then the warning triggers. The bug can be reproduced reliably when the work
delay is increased.

Flush the optimizer work and wait for the optimizing/unoptimizing lists to
become empty before returning from the kprobes tracer selftest. That
ensures that all operations which were queued due to the probes removal
have completed.

Link: http://lkml.kernel.org/r/20170516094802.76a468bb@gandalf.local.home

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 6274de498 ("kprobes: Support delayed unoptimizing")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 include/linux/kprobes.h     |    4 +++-
 kernel/kprobes.c            |    2 +-
 kernel/trace/trace_kprobe.c |    5 +++++
 3 files changed, 9 insertions(+), 2 deletions(-)

--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -330,7 +330,9 @@ extern int proc_kprobes_optimization_han
 					     int write, void __user *buffer,
 					     size_t *length, loff_t *ppos);
 #endif
-
+extern void wait_for_kprobe_optimizer(void);
+#else
+static inline void wait_for_kprobe_optimizer(void) { }
 #endif /* CONFIG_OPTPROBES */
 #ifdef CONFIG_KPROBES_ON_FTRACE
 extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -563,7 +563,7 @@ static void kprobe_optimizer(struct work
 }
 
 /* Wait for completing optimization and unoptimization */
-static void wait_for_kprobe_optimizer(void)
+void wait_for_kprobe_optimizer(void)
 {
 	mutex_lock(&kprobe_mutex);
 
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1484,6 +1484,11 @@ static __init int kprobe_trace_self_test
 
 end:
 	release_all_trace_kprobes();
+	/*
+	 * Wait for the optimizer work to finish. Otherwise it might fiddle
+	 * with probes in already freed __init text.
+	 */
+	wait_for_kprobe_optimizer();
 	if (warn)
 		pr_cont("NG: Some tests are failed. Please check them.\n");
 	else


Patches currently in stable-queue which might be from tglx@linutronix.de are

queue-4.9/stackprotector-increase-the-per-task-stack-canary-s-random-range-from-32-bits-to-64-bits-on-64-bit-platforms.patch
queue-4.9/genirq-fix-chained-interrupt-data-ordering.patch
queue-4.9/tracing-kprobes-enforce-kprobes-teardown-after-testing.patch