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Subject[for-next][PATCH 2/3] ftrace: Fix regression with module command in stack_trace_filter
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

When doing the following command:

# echo ":mod:kvm_intel" > /sys/kernel/tracing/stack_trace_filter

it triggered a crash.

This happened with the clean up of probes. It required all callers to the
regex function (doing ftrace filtering) to have ops->private be a pointer to
a trace_array. But for the stack tracer, that is not the case.

Allow for the ops->private to be NULL, and change the function command
callbacks to handle the trace_array pointer being NULL as well.

Fixes: d2afd57a4b96 ("tracing/ftrace: Allow instances to have their own function probes")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/ftrace.c | 3 ---
kernel/trace/trace.c | 3 +++
kernel/trace/trace_functions.c | 12 ++++++++++++
kernel/trace/trace_stack.c | 6 ++++--
4 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 9e5841dc14b5..b308be30dfb9 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4337,9 +4337,6 @@ static int ftrace_process_regex(struct ftrace_iterator *iter,

command = strsep(&next, ":");

- if (WARN_ON_ONCE(!tr))
- return -EINVAL;
-
mutex_lock(&ftrace_cmd_mutex);
list_for_each_entry(p, &ftrace_commands, list) {
if (strcmp(p->name, command) == 0) {
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1122f151466f..091e801145c9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6881,6 +6881,9 @@ ftrace_trace_snapshot_callback(struct trace_array *tr, struct ftrace_hash *hash,
char *number;
int ret;

+ if (!tr)
+ return -ENODEV;
+
/* hash funcs only work with set_ftrace_filter */
if (!enable)
return -EINVAL;
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index a3bddbfd0874..a0910c0cdf2e 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -654,6 +654,9 @@ ftrace_trace_onoff_callback(struct trace_array *tr, struct ftrace_hash *hash,
{
struct ftrace_probe_ops *ops;

+ if (!tr)
+ return -ENODEV;
+
/* we register both traceon and traceoff to this callback */
if (strcmp(cmd, "traceon") == 0)
ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
@@ -670,6 +673,9 @@ ftrace_stacktrace_callback(struct trace_array *tr, struct ftrace_hash *hash,
{
struct ftrace_probe_ops *ops;

+ if (!tr)
+ return -ENODEV;
+
ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;

return ftrace_trace_probe_callback(tr, ops, hash, glob, cmd,
@@ -682,6 +688,9 @@ ftrace_dump_callback(struct trace_array *tr, struct ftrace_hash *hash,
{
struct ftrace_probe_ops *ops;

+ if (!tr)
+ return -ENODEV;
+
ops = &dump_probe_ops;

/* Only dump once. */
@@ -695,6 +704,9 @@ ftrace_cpudump_callback(struct trace_array *tr, struct ftrace_hash *hash,
{
struct ftrace_probe_ops *ops;

+ if (!tr)
+ return -ENODEV;
+
ops = &cpudump_probe_ops;

/* Only dump once. */
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 76aa04d4c925..b4a751e8f9d6 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -409,7 +409,9 @@ static const struct file_operations stack_trace_fops = {
static int
stack_trace_filter_open(struct inode *inode, struct file *file)
{
- return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
+ struct ftrace_ops *ops = inode->i_private;
+
+ return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
inode, file);
}

@@ -476,7 +478,7 @@ static __init int stack_trace_init(void)
NULL, &stack_trace_fops);

trace_create_file("stack_trace_filter", 0444, d_tracer,
- NULL, &stack_trace_filter_fops);
+ &trace_ops, &stack_trace_filter_fops);

if (stack_trace_filter_buf[0])
ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
--
2.10.2

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