[PATCH v2 02/18] tracing/remotes: Release tracefs,eventfs on registration failure
From: Vincent Donnefort
Date: Fri Jun 05 2026 - 12:46:23 EST
In trace_remote_register(), if registration of events or the init
callback fails, the created tracefs and eventfs directories are leaked.
Release the entire eventfs and tracefs hierarchy on trace_remote
registration failure.
Signed-off-by: Vincent Donnefort <vdonnefort@xxxxxxxxxx>
diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
index 9f1669d433d5..9b27c7bd6040 100644
--- a/kernel/trace/trace_remote.c
+++ b/kernel/trace/trace_remote.c
@@ -45,7 +45,8 @@ struct trace_remote {
struct trace_buffer *trace_buffer;
struct trace_buffer_desc *trace_buffer_desc;
struct dentry *dentry;
- struct eventfs_inode *eventfs;
+ struct eventfs_inode *eventfs_root;
+ struct eventfs_inode *eventfs_subdir;
struct remote_event *events;
unsigned long nr_events;
unsigned long trace_buffer_size;
@@ -60,6 +61,7 @@ struct trace_remote {
static DEFINE_MUTEX(trace_remotes_lock);
static LIST_HEAD(trace_remotes);
+static struct dentry *trace_remotes_root;
static bool trace_remote_loaded(struct trace_remote *remote)
{
@@ -865,23 +867,21 @@ static const struct file_operations trace_fops = {
static int trace_remote_init_tracefs(const char *name, struct trace_remote *remote)
{
struct dentry *remote_d, *percpu_d, *d;
- static struct dentry *root;
- static DEFINE_MUTEX(lock);
bool root_inited = false;
int cpu;
- guard(mutex)(&lock);
+ lockdep_assert_held(&trace_remotes_lock);
- if (!root) {
- root = tracefs_create_dir(TRACEFS_DIR, NULL);
- if (!root) {
+ if (!trace_remotes_root) {
+ trace_remotes_root = tracefs_create_dir(TRACEFS_DIR, NULL);
+ if (!trace_remotes_root) {
pr_err("Failed to create tracefs dir "TRACEFS_DIR"\n");
return -ENOMEM;
}
root_inited = true;
}
- remote_d = tracefs_create_dir(name, root);
+ remote_d = tracefs_create_dir(name, trace_remotes_root);
if (!remote_d) {
pr_err("Failed to create tracefs dir "TRACEFS_DIR"%s/\n", name);
goto err;
@@ -939,8 +939,8 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo
err:
if (root_inited) {
- tracefs_remove(root);
- root = NULL;
+ tracefs_remove(trace_remotes_root);
+ trace_remotes_root = NULL;
} else {
tracefs_remove(remote_d);
}
@@ -948,8 +948,26 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo
return -ENOMEM;
}
+static void trace_remote_remove_tracefs(struct trace_remote *remote)
+{
+ lockdep_assert_held(&trace_remotes_lock);
+
+ if (!remote->dentry)
+ return;
+
+ tracefs_remove(remote->dentry);
+ remote->dentry = NULL;
+
+ if (!list_empty(&trace_remotes))
+ return;
+
+ tracefs_remove(trace_remotes_root);
+ trace_remotes_root = NULL;
+}
+
static int trace_remote_register_events(const char *remote_name, struct trace_remote *remote,
struct remote_event *events, size_t nr_events);
+static void trace_remote_unregister_events(struct trace_remote *remote);
/**
* trace_remote_register() - Register a Tracefs remote
@@ -972,10 +990,9 @@ static int trace_remote_register_events(const char *remote_name, struct trace_re
int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv,
struct remote_event *events, size_t nr_events)
{
- struct trace_remote *remote;
+ struct trace_remote *remote __free(kfree) = kzalloc_obj(*remote);
int ret;
- remote = kzalloc_obj(*remote);
if (!remote)
return -ENOMEM;
@@ -986,13 +1003,15 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs,
mutex_init(&remote->lock);
init_rwsem(&remote->reader_lock);
- if (trace_remote_init_tracefs(name, remote)) {
- kfree(remote);
- return -ENOMEM;
- }
+ guard(mutex)(&trace_remotes_lock);
+
+ ret = trace_remote_init_tracefs(name, remote);
+ if (ret)
+ return ret;
ret = trace_remote_register_events(name, remote, events, nr_events);
if (ret) {
+ trace_remote_remove_tracefs(remote);
pr_err("Failed to register events for trace remote '%s' (%d)\n",
name, ret);
return ret;
@@ -1000,13 +1019,16 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs,
ret = cbs->init ? cbs->init(remote->dentry, priv) : 0;
if (ret) {
+ trace_remote_unregister_events(remote);
+ trace_remote_remove_tracefs(remote);
pr_err("Init failed for trace remote '%s' (%d)\n", name, ret);
- } else {
- guard(mutex)(&trace_remotes_lock);
- list_add(&remote->node, &trace_remotes);
+ return ret;
}
- return ret;
+ list_add(&remote->node, &trace_remotes);
+ retain_and_null_ptr(remote);
+
+ return 0;
}
EXPORT_SYMBOL_GPL(trace_remote_register);
@@ -1341,7 +1363,6 @@ static int remote_events_dir_callback(const char *name, umode_t *mode, void **da
static int trace_remote_init_eventfs(const char *remote_name, struct trace_remote *remote,
struct remote_event *evt)
{
- struct eventfs_inode *eventfs = remote->eventfs;
static struct eventfs_entry dir_entries[] = {
{
.name = "enable",
@@ -1366,35 +1387,37 @@ static int trace_remote_init_eventfs(const char *remote_name, struct trace_remot
.callback = remote_event_callback,
}
};
- bool eventfs_create = false;
+ struct eventfs_inode *eventfs_root, *eventfs_subdir, *e;
- if (!eventfs) {
- eventfs = eventfs_create_events_dir("events", remote->dentry, dir_entries,
- ARRAY_SIZE(dir_entries), remote);
- if (IS_ERR(eventfs))
- return PTR_ERR(eventfs);
+ eventfs_root = remote->eventfs_root;
+ eventfs_subdir = remote->eventfs_subdir;
+ if (!eventfs_root) {
+ eventfs_root = eventfs_create_events_dir("events", remote->dentry, dir_entries,
+ ARRAY_SIZE(dir_entries), remote);
+ if (IS_ERR(eventfs_root))
+ return PTR_ERR(eventfs_root);
/*
* Create similar hierarchy as local events even if a single system is supported at
* the moment
*/
- eventfs = eventfs_create_dir(remote_name, eventfs, NULL, 0, NULL);
- if (IS_ERR(eventfs))
- return PTR_ERR(eventfs);
-
- remote->eventfs = eventfs;
- eventfs_create = true;
+ eventfs_subdir = eventfs_create_dir(remote_name, eventfs_root, NULL, 0, NULL);
+ if (IS_ERR(eventfs_subdir)) {
+ eventfs_remove_events_dir(eventfs_root);
+ return PTR_ERR(eventfs_subdir);
+ }
}
- eventfs = eventfs_create_dir(evt->name, eventfs, entries, ARRAY_SIZE(entries), evt);
- if (IS_ERR(eventfs)) {
- if (eventfs_create) {
- eventfs_remove_events_dir(remote->eventfs);
- remote->eventfs = NULL;
- }
- return PTR_ERR(eventfs);
+ e = eventfs_create_dir(evt->name, eventfs_subdir, entries, ARRAY_SIZE(entries), evt);
+ if (IS_ERR(e)) {
+ if (!remote->eventfs_root)
+ eventfs_remove_events_dir(eventfs_root);
+ return PTR_ERR(e);
}
+ remote->eventfs_root = eventfs_root;
+ remote->eventfs_subdir = eventfs_subdir;
+
return 0;
}
@@ -1409,11 +1432,11 @@ static int trace_remote_attach_events(struct trace_remote *remote, struct remote
if (evt->remote)
return -EEXIST;
- evt->remote = remote;
-
/* We need events to be sorted for efficient lookup */
if (i && evt->id <= events[i - 1].id)
return -EINVAL;
+
+ evt->remote = remote;
}
remote->events = events;
@@ -1422,14 +1445,33 @@ static int trace_remote_attach_events(struct trace_remote *remote, struct remote
return 0;
}
+static void trace_remote_detach_events(struct trace_remote *remote, struct remote_event *events,
+ size_t nr_events)
+{
+ int i;
+
+ for (i = 0; i < nr_events; i++) {
+ struct remote_event *evt = &events[i];
+
+ if (evt->remote == remote)
+ evt->remote = NULL;
+ }
+
+ remote->events = NULL;
+ remote->nr_events = 0;
+}
+
static int trace_remote_register_events(const char *remote_name, struct trace_remote *remote,
struct remote_event *events, size_t nr_events)
{
int i, ret;
ret = trace_remote_attach_events(remote, events, nr_events);
- if (ret)
+ if (ret) {
+ /* It is safe to call detach on a half-registered array */
+ trace_remote_detach_events(remote, events, nr_events);
return ret;
+ }
for (i = 0; i < nr_events; i++) {
struct remote_event *evt = &events[i];
@@ -1443,6 +1485,13 @@ static int trace_remote_register_events(const char *remote_name, struct trace_re
return 0;
}
+static void trace_remote_unregister_events(struct trace_remote *remote)
+{
+ trace_remote_detach_events(remote, remote->events, remote->nr_events);
+ if (remote->eventfs_root)
+ eventfs_remove_events_dir(remote->eventfs_root);
+}
+
static int __cmp_events(const void *key, const void *data)
{
const struct remote_event *evt = data;
--
2.54.0.1032.g2f8565e1d1-goog