Commit ba27d855 authored by Jakob Koschel's avatar Jakob Koschel Committed by Steven Rostedt (Google)
Browse files

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://lkml.kernel.org/r/20220427170734.819891-5-jakobkoschel@gmail.com

Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/


Signed-off-by: default avatarJakob Koschel <jakobkoschel@gmail.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 45e333ce

kernel/trace/ftrace.c

+12 −8
Original line number Original line Diff line number Diff line
@@ -4560,8 +4560,8 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr, 
			       struct ftrace_probe_ops *probe_ops,

			       struct ftrace_probe_ops *probe_ops,

			       void *data)

			       void *data)

{

{

	struct ftrace_func_probe *probe = NULL, *iter;

	struct ftrace_func_entry *entry;

	struct ftrace_func_entry *entry;

	struct ftrace_func_probe *probe;

	struct ftrace_hash **orig_hash;

	struct ftrace_hash **orig_hash;

	struct ftrace_hash *old_hash;

	struct ftrace_hash *old_hash;

	struct ftrace_hash *hash;

	struct ftrace_hash *hash;
@@ -4580,11 +4580,13 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr, 




	mutex_lock(&ftrace_lock);

	mutex_lock(&ftrace_lock);

	/* Check if the probe_ops is already registered */

	/* Check if the probe_ops is already registered */

	list_for_each_entry(probe, &tr->func_probes, list) {

	list_for_each_entry(iter, &tr->func_probes, list) {

		if (probe->probe_ops == probe_ops)

		if (iter->probe_ops == probe_ops) {

			probe = iter;

			break;

			break;

		}

		}

	if (&probe->list == &tr->func_probes) {

	}

	if (!probe) {

		probe = kzalloc(sizeof(*probe), GFP_KERNEL);

		probe = kzalloc(sizeof(*probe), GFP_KERNEL);

		if (!probe) {

		if (!probe) {

			mutex_unlock(&ftrace_lock);

			mutex_unlock(&ftrace_lock);
@@ -4702,9 +4704,9 @@ int 
unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,

unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,

				      struct ftrace_probe_ops *probe_ops)

				      struct ftrace_probe_ops *probe_ops)

{

{

	struct ftrace_func_probe *probe = NULL, *iter;

	struct ftrace_ops_hash old_hash_ops;

	struct ftrace_ops_hash old_hash_ops;

	struct ftrace_func_entry *entry;

	struct ftrace_func_entry *entry;

	struct ftrace_func_probe *probe;

	struct ftrace_glob func_g;

	struct ftrace_glob func_g;

	struct ftrace_hash **orig_hash;

	struct ftrace_hash **orig_hash;

	struct ftrace_hash *old_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);

	mutex_lock(&ftrace_lock);

	/* Check if the probe_ops is already registered */

	/* Check if the probe_ops is already registered */

	list_for_each_entry(probe, &tr->func_probes, list) {

	list_for_each_entry(iter, &tr->func_probes, list) {

		if (probe->probe_ops == probe_ops)

		if (iter->probe_ops == probe_ops) {

			probe = iter;

			break;

			break;

		}

		}

	if (&probe->list == &tr->func_probes)

	}

	if (!probe)

		goto err_unlock_ftrace;

		goto err_unlock_ftrace;





	ret = -EINVAL;

	ret = -EINVAL;

kernel/trace/trace_eprobe.c

+8 −6
Original line number Original line Diff line number Diff line
@@ -648,7 +648,7 @@ static struct trace_event_functions eprobe_funcs = { 
static int disable_eprobe(struct trace_eprobe *ep,

static int disable_eprobe(struct trace_eprobe *ep,

			  struct trace_array *tr)

			  struct trace_array *tr)

{

{

	struct event_trigger_data *trigger;

	struct event_trigger_data *trigger = NULL, *iter;

	struct trace_event_file *file;

	struct trace_event_file *file;

	struct eprobe_data *edata;

	struct eprobe_data *edata;
@@ -656,14 +656,16 @@ static int disable_eprobe(struct trace_eprobe *ep, 
	if (!file)

	if (!file)

		return -ENOENT;

		return -ENOENT;





	list_for_each_entry(trigger, &file->triggers, list) {

	list_for_each_entry(iter, &file->triggers, list) {

		if (!(trigger->flags & EVENT_TRIGGER_FL_PROBE))

		if (!(iter->flags & EVENT_TRIGGER_FL_PROBE))

			continue;

			continue;

		edata = trigger->private_data;

		edata = iter->private_data;

		if (edata->ep == ep)

		if (edata->ep == ep) {

			trigger = iter;

			break;

			break;

		}

		}

	if (list_entry_is_head(trigger, &file->triggers, list))

	}

	if (!trigger)

		return -ENODEV;

		return -ENODEV;





	list_del_rcu(&trigger->list);

	list_del_rcu(&trigger->list);

kernel/trace/trace_events.c

+6 −6
Original line number Original line Diff line number Diff line
@@ -2279,8 +2279,8 @@ static struct dentry * 
event_subsystem_dir(struct trace_array *tr, const char *name,

event_subsystem_dir(struct trace_array *tr, const char *name,

		    struct trace_event_file *file, struct dentry *parent)

		    struct trace_event_file *file, struct dentry *parent)

{

{

	struct event_subsystem *system, *iter;

	struct trace_subsystem_dir *dir;

	struct trace_subsystem_dir *dir;

	struct event_subsystem *system;

	struct dentry *entry;

	struct dentry *entry;





	/* First see if we did not already create this dir */

	/* 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. */

	/* Now see if the system itself exists. */

	list_for_each_entry(system, &event_subsystems, list) {

	system = NULL;

		if (strcmp(system->name, name) == 0)

	list_for_each_entry(iter, &event_subsystems, list) {

		if (strcmp(iter->name, name) == 0) {

			system = iter;

			break;

			break;

		}

		}

	/* Reset system variable when not found */

	}

	if (&system->list == &event_subsystems)

		system = NULL;





	dir = kmalloc(sizeof(*dir), GFP_KERNEL);

	dir = kmalloc(sizeof(*dir), GFP_KERNEL);

	if (!dir)

	if (!dir)