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-rw-r--r--fs/tracefs/event_inode.c45
-rw-r--r--fs/tracefs/internal.h3
2 files changed, 41 insertions, 7 deletions
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index dd5971855732..e9625732c52d 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -24,7 +24,20 @@
#include <linux/delay.h>
#include "internal.h"
+/*
+ * eventfs_mutex protects the eventfs_inode (ei) dentry. Any access
+ * to the ei->dentry must be done under this mutex and after checking
+ * if ei->is_freed is not set. The ei->dentry is released under the
+ * mutex at the same time ei->is_freed is set. If ei->is_freed is set
+ * then the ei->dentry is invalid.
+ */
static DEFINE_MUTEX(eventfs_mutex);
+
+/*
+ * The eventfs_inode (ei) itself is protected by SRCU. It is released from
+ * its parent's list and will have is_freed set (under eventfs_mutex).
+ * After the SRCU grace period is over, the ei may be freed.
+ */
DEFINE_STATIC_SRCU(eventfs_srcu);
static struct dentry *eventfs_root_lookup(struct inode *dir,
@@ -239,6 +252,10 @@ create_file_dentry(struct eventfs_inode *ei, struct dentry **e_dentry,
bool invalidate = false;
mutex_lock(&eventfs_mutex);
+ if (ei->is_freed) {
+ mutex_unlock(&eventfs_mutex);
+ return NULL;
+ }
/* If the e_dentry already has a dentry, use it */
if (*e_dentry) {
/* lookup does not need to up the ref count */
@@ -312,6 +329,8 @@ static void eventfs_post_create_dir(struct eventfs_inode *ei)
struct eventfs_inode *ei_child;
struct tracefs_inode *ti;
+ lockdep_assert_held(&eventfs_mutex);
+
/* srcu lock already held */
/* fill parent-child relation */
list_for_each_entry_srcu(ei_child, &ei->children, list,
@@ -325,6 +344,7 @@ static void eventfs_post_create_dir(struct eventfs_inode *ei)
/**
* create_dir_dentry - Create a directory dentry for the eventfs_inode
+ * @pei: The eventfs_inode parent of ei.
* @ei: The eventfs_inode to create the directory for
* @parent: The dentry of the parent of this directory
* @lookup: True if this is called by the lookup code
@@ -332,12 +352,17 @@ static void eventfs_post_create_dir(struct eventfs_inode *ei)
* This creates and attaches a directory dentry to the eventfs_inode @ei.
*/
static struct dentry *
-create_dir_dentry(struct eventfs_inode *ei, struct dentry *parent, bool lookup)
+create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
+ struct dentry *parent, bool lookup)
{
bool invalidate = false;
struct dentry *dentry = NULL;
mutex_lock(&eventfs_mutex);
+ if (pei->is_freed || ei->is_freed) {
+ mutex_unlock(&eventfs_mutex);
+ return NULL;
+ }
if (ei->dentry) {
/* If the dentry already has a dentry, use it */
dentry = ei->dentry;
@@ -440,7 +465,7 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
*/
mutex_lock(&eventfs_mutex);
ei = READ_ONCE(ti->private);
- if (ei)
+ if (ei && !ei->is_freed)
ei_dentry = READ_ONCE(ei->dentry);
mutex_unlock(&eventfs_mutex);
@@ -454,7 +479,7 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
if (strcmp(ei_child->name, name) != 0)
continue;
ret = simple_lookup(dir, dentry, flags);
- create_dir_dentry(ei_child, ei_dentry, true);
+ create_dir_dentry(ei, ei_child, ei_dentry, true);
created = true;
break;
}
@@ -588,7 +613,7 @@ static int dcache_dir_open_wrapper(struct inode *inode, struct file *file)
list_for_each_entry_srcu(ei_child, &ei->children, list,
srcu_read_lock_held(&eventfs_srcu)) {
- d = create_dir_dentry(ei_child, parent, false);
+ d = create_dir_dentry(ei, ei_child, parent, false);
if (d) {
ret = add_dentries(&dentries, d, cnt);
if (ret < 0)
@@ -705,12 +730,20 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode
ei->nr_entries = size;
ei->data = data;
INIT_LIST_HEAD(&ei->children);
+ INIT_LIST_HEAD(&ei->list);
mutex_lock(&eventfs_mutex);
- list_add_tail(&ei->list, &parent->children);
- ei->d_parent = parent->dentry;
+ if (!parent->is_freed) {
+ list_add_tail(&ei->list, &parent->children);
+ ei->d_parent = parent->dentry;
+ }
mutex_unlock(&eventfs_mutex);
+ /* Was the parent freed? */
+ if (list_empty(&ei->list)) {
+ free_ei(ei);
+ ei = NULL;
+ }
return ei;
}
diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h
index c7d88aaa949f..5a98e87dd3d1 100644
--- a/fs/tracefs/internal.h
+++ b/fs/tracefs/internal.h
@@ -24,6 +24,7 @@ struct tracefs_inode {
* @d_children: The array of dentries to represent the files when created
* @data: The private data to pass to the callbacks
* @is_freed: Flag set if the eventfs is on its way to be freed
+ * Note if is_freed is set, then dentry is corrupted.
* @nr_entries: The number of items in @entries
*/
struct eventfs_inode {
@@ -31,7 +32,7 @@ struct eventfs_inode {
const struct eventfs_entry *entries;
const char *name;
struct list_head children;
- struct dentry *dentry;
+ struct dentry *dentry; /* Check is_freed to access */
struct dentry *d_parent;
struct dentry **d_children;
void *data;