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Message-Id: <20220427170734.819891-5-jakobkoschel@gmail.com>
Date: Wed, 27 Apr 2022 19:07:34 +0200
From: Jakob Koschel <jakobkoschel@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
Jakob Koschel <jakobkoschel@...il.com>
Subject: [PATCH v2 4/4] tracing: Remove check of list iterator against head past the loop body
When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.
While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.
In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].
Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
kernel/trace/ftrace.c | 20 ++++++++++++--------
kernel/trace/trace_eprobe.c | 14 ++++++++------
kernel/trace/trace_events.c | 12 ++++++------
3 files changed, 26 insertions(+), 20 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4f1d2f5e7263..5c465e70d146 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4560,8 +4560,8 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
struct ftrace_probe_ops *probe_ops,
void *data)
{
+ struct ftrace_func_probe *probe = NULL, *iter;
struct ftrace_func_entry *entry;
- struct ftrace_func_probe *probe;
struct ftrace_hash **orig_hash;
struct ftrace_hash *old_hash;
struct ftrace_hash *hash;
@@ -4580,11 +4580,13 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
mutex_lock(&ftrace_lock);
/* Check if the probe_ops is already registered */
- list_for_each_entry(probe, &tr->func_probes, list) {
- if (probe->probe_ops == probe_ops)
+ list_for_each_entry(iter, &tr->func_probes, list) {
+ if (iter->probe_ops == probe_ops) {
+ probe = iter;
break;
+ }
}
- if (&probe->list == &tr->func_probes) {
+ if (!probe) {
probe = kzalloc(sizeof(*probe), GFP_KERNEL);
if (!probe) {
mutex_unlock(&ftrace_lock);
@@ -4702,9 +4704,9 @@ int
unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
struct ftrace_probe_ops *probe_ops)
{
+ struct ftrace_func_probe *probe = NULL, *iter;
struct ftrace_ops_hash old_hash_ops;
struct ftrace_func_entry *entry;
- struct ftrace_func_probe *probe;
struct ftrace_glob func_g;
struct ftrace_hash **orig_hash;
struct ftrace_hash *old_hash;
@@ -4732,11 +4734,13 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
mutex_lock(&ftrace_lock);
/* Check if the probe_ops is already registered */
- list_for_each_entry(probe, &tr->func_probes, list) {
- if (probe->probe_ops == probe_ops)
+ list_for_each_entry(iter, &tr->func_probes, list) {
+ if (iter->probe_ops == probe_ops) {
+ probe = iter;
break;
+ }
}
- if (&probe->list == &tr->func_probes)
+ if (!probe)
goto err_unlock_ftrace;
ret = -EINVAL;
diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index 541aa13581b9..63e901a28425 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -650,7 +650,7 @@ static struct trace_event_functions eprobe_funcs = {
static int disable_eprobe(struct trace_eprobe *ep,
struct trace_array *tr)
{
- struct event_trigger_data *trigger;
+ struct event_trigger_data *trigger = NULL, *iter;
struct trace_event_file *file;
struct eprobe_data *edata;
@@ -658,14 +658,16 @@ static int disable_eprobe(struct trace_eprobe *ep,
if (!file)
return -ENOENT;
- list_for_each_entry(trigger, &file->triggers, list) {
- if (!(trigger->flags & EVENT_TRIGGER_FL_PROBE))
+ list_for_each_entry(iter, &file->triggers, list) {
+ if (!(iter->flags & EVENT_TRIGGER_FL_PROBE))
continue;
- edata = trigger->private_data;
- if (edata->ep == ep)
+ edata = iter->private_data;
+ if (edata->ep == ep) {
+ trigger = iter;
break;
+ }
}
- if (list_entry_is_head(trigger, &file->triggers, list))
+ if (!trigger)
return -ENODEV;
list_del_rcu(&trigger->list);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e4a442060707..78f313b7b315 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2279,8 +2279,8 @@ static struct dentry *
event_subsystem_dir(struct trace_array *tr, const char *name,
struct trace_event_file *file, struct dentry *parent)
{
+ struct event_subsystem *system, *iter;
struct trace_subsystem_dir *dir;
- struct event_subsystem *system;
struct dentry *entry;
/* First see if we did not already create this dir */
@@ -2294,13 +2294,13 @@ event_subsystem_dir(struct trace_array *tr, const char *name,
}
/* Now see if the system itself exists. */
- list_for_each_entry(system, &event_subsystems, list) {
- if (strcmp(system->name, name) == 0)
+ system = NULL;
+ list_for_each_entry(iter, &event_subsystems, list) {
+ if (strcmp(iter->name, name) == 0) {
+ system = iter;
break;
+ }
}
- /* Reset system variable when not found */
- if (&system->list == &event_subsystems)
- system = NULL;
dir = kmalloc(sizeof(*dir), GFP_KERNEL);
if (!dir)
--
2.25.1
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