From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Wed, 10 Feb 2021 14:14:59 +0000 (+0100)
Subject: 4.14-stable patches
X-Git-Tag: v4.19.176~28
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=50d2a028593ee14efb8e47ebbbf48aec46af6820;p=thirdparty%2Fkernel%2Fstable-queue.git

4.14-stable patches

added patches:
	fgraph-initialize-tracing_graph_pause-at-task-creation.patch
---

diff --git a/queue-4.14/fgraph-initialize-tracing_graph_pause-at-task-creation.patch b/queue-4.14/fgraph-initialize-tracing_graph_pause-at-task-creation.patch
new file mode 100644
index 00000000000..f551977d7e4
--- /dev/null
+++ b/queue-4.14/fgraph-initialize-tracing_graph_pause-at-task-creation.patch
@@ -0,0 +1,83 @@
+From 7e0a9220467dbcfdc5bc62825724f3e52e50ab31 Mon Sep 17 00:00:00 2001
+From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
+Date: Fri, 29 Jan 2021 10:13:53 -0500
+Subject: fgraph: Initialize tracing_graph_pause at task creation
+
+From: Steven Rostedt (VMware) <rostedt@goodmis.org>
+
+commit 7e0a9220467dbcfdc5bc62825724f3e52e50ab31 upstream.
+
+On some archs, the idle task can call into cpu_suspend(). The cpu_suspend()
+will disable or pause function graph tracing, as there's some paths in
+bringing down the CPU that can have issues with its return address being
+modified. The task_struct structure has a "tracing_graph_pause" atomic
+counter, that when set to something other than zero, the function graph
+tracer will not modify the return address.
+
+The problem is that the tracing_graph_pause counter is initialized when the
+function graph tracer is enabled. This can corrupt the counter for the idle
+task if it is suspended in these architectures.
+
+   CPU 1				CPU 2
+   -----				-----
+  do_idle()
+    cpu_suspend()
+      pause_graph_tracing()
+          task_struct->tracing_graph_pause++ (0 -> 1)
+
+				start_graph_tracing()
+				  for_each_online_cpu(cpu) {
+				    ftrace_graph_init_idle_task(cpu)
+				      task-struct->tracing_graph_pause = 0 (1 -> 0)
+
+      unpause_graph_tracing()
+          task_struct->tracing_graph_pause-- (0 -> -1)
+
+The above should have gone from 1 to zero, and enabled function graph
+tracing again. But instead, it is set to -1, which keeps it disabled.
+
+There's no reason that the field tracing_graph_pause on the task_struct can
+not be initialized at boot up.
+
+Cc: stable@vger.kernel.org
+Fixes: 380c4b1411ccd ("tracing/function-graph-tracer: append the tracing_graph_flag")
+Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211339
+Reported-by: pierre.gondois@arm.com
+Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ include/linux/ftrace.h |    4 +++-
+ kernel/trace/ftrace.c  |    2 --
+ 2 files changed, 3 insertions(+), 3 deletions(-)
+
+--- a/include/linux/ftrace.h
++++ b/include/linux/ftrace.h
+@@ -792,7 +792,9 @@ typedef int (*trace_func_graph_ent_t)(st
+ #ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ 
+ /* for init task */
+-#define INIT_FTRACE_GRAPH		.ret_stack = NULL,
++#define INIT_FTRACE_GRAPH				\
++	.ret_stack		= NULL,			\
++	.tracing_graph_pause	= ATOMIC_INIT(0),
+ 
+ /*
+  * Stack of return addresses for functions
+--- a/kernel/trace/ftrace.c
++++ b/kernel/trace/ftrace.c
+@@ -6666,7 +6666,6 @@ static int alloc_retstack_tasklist(struc
+ 		}
+ 
+ 		if (t->ret_stack == NULL) {
+-			atomic_set(&t->tracing_graph_pause, 0);
+ 			atomic_set(&t->trace_overrun, 0);
+ 			t->curr_ret_stack = -1;
+ 			/* Make sure the tasks see the -1 first: */
+@@ -6878,7 +6877,6 @@ static DEFINE_PER_CPU(struct ftrace_ret_
+ static void
+ graph_init_task(struct task_struct *t, struct ftrace_ret_stack *ret_stack)
+ {
+-	atomic_set(&t->tracing_graph_pause, 0);
+ 	atomic_set(&t->trace_overrun, 0);
+ 	t->ftrace_timestamp = 0;
+ 	/* make curr_ret_stack visible before we add the ret_stack */