Patch "tracing: Call clear_boot_tracer() at lateinit_sync" has been added to the 4.12-stable tree

Patch "tracing: Call clear_boot_tracer() at lateinit_sync" has been added to the 4.12-stable tree

[gregkh]

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

    tracing: Call clear_boot_tracer() at lateinit_sync

to the 4.12-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-call-clear_boot_tracer-at-lateinit_sync.patch
and it can be found in the queue-4.12 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 4bb0f0e73c8c30917d169c4a0f1ac083690c545b Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Date: Tue, 1 Aug 2017 12:01:52 -0400
Subject: tracing: Call clear_boot_tracer() at lateinit_sync

From: Steven Rostedt (VMware) <rostedt@goodmis.org>

commit 4bb0f0e73c8c30917d169c4a0f1ac083690c545b upstream.

The clear_boot_tracer function is used to reset the default_bootup_tracer
string to prevent it from being accessed after boot, as it originally points
to init data. But since clear_boot_tracer() is called via the
init_lateinit() call, it races with the initcall for registering the hwlat
tracer. If someone adds "ftrace=hwlat" to the kernel command line, depending
on how the linker sets up the text, the saved command line may be cleared,
and the hwlat tracer never is initialized.

Simply have the clear_boot_tracer() be called by initcall_lateinit_sync() as
that's for tasks to be called after lateinit.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=196551

Fixes: e7c15cd8a ("tracing: Added hardware latency tracer")
Reported-by: Zamir SUN <sztsian@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/trace/trace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -8224,4 +8224,4 @@ __init static int clear_boot_tracer(void
 }
 
 fs_initcall(tracer_init_tracefs);
-late_initcall(clear_boot_tracer);
+late_initcall_sync(clear_boot_tracer);


Patches currently in stable-queue which might be from rostedt@goodmis.org are

queue-4.12/tracing-missing-error-code-in-tracer_alloc_buffers.patch
queue-4.12/ring-buffer-have-ring_buffer_alloc_read_page-return-error-on-offline-cpu.patch
queue-4.12/ftrace-check-for-null-ret_stack-on-profile-function-graph-entry-function.patch
queue-4.12/tracing-fix-freeing-of-filter-in-create_filter-when-set_str-is-false.patch
queue-4.12/tracing-call-clear_boot_tracer-at-lateinit_sync.patch
queue-4.12/tracing-fix-kmemleak-in-tracing_map_array_free.patch