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Subject[PATCH 3/3] audit: clean up refcounting in audit-tree
Date
From: Miklos Szeredi <mszeredi@suse.cz>

Drop the initial reference by fsnotify_init_mark early instead of
audit_tree_freeing_mark() at destroy time.

In the cases we destroy the mark before we drop the initial reference we need to
get rid of the get_mark that balances the put_mark in audit_tree_freeing_mark().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
kernel/audit_tree.c | 12 +++++++++---
1 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 31fdc48..7b95706 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -292,6 +292,7 @@ static void untag_chunk(struct node *p)
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
fsnotify_destroy_mark(entry);
+ fsnotify_put_mark(&new->mark); /* drop initial reference */
goto out;

Fallback:
@@ -330,7 +331,6 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
spin_unlock(&hash_lock);
chunk->dead = 1;
spin_unlock(&entry->lock);
- fsnotify_get_mark(entry);
fsnotify_destroy_mark(entry);
fsnotify_put_mark(entry);
return 0;
@@ -346,6 +346,7 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
insert_hash(chunk);
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
+ fsnotify_put_mark(entry); /* drop initial reference */
return 0;
}

@@ -411,7 +412,6 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
spin_unlock(&chunk_entry->lock);
spin_unlock(&old_entry->lock);

- fsnotify_get_mark(chunk_entry);
fsnotify_destroy_mark(chunk_entry);

fsnotify_put_mark(chunk_entry);
@@ -444,6 +444,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
spin_unlock(&chunk_entry->lock);
spin_unlock(&old_entry->lock);
fsnotify_destroy_mark(old_entry);
+ fsnotify_put_mark(chunk_entry); /* drop initial reference */
fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
return 0;
}
@@ -915,7 +916,12 @@ static void audit_tree_freeing_mark(struct fsnotify_mark *entry, struct fsnotify
struct audit_chunk *chunk = container_of(entry, struct audit_chunk, mark);

evict_chunk(chunk);
- fsnotify_put_mark(entry);
+
+ /*
+ * We are guaranteed to have at least one reference to the mark from
+ * either the inode or the caller of fsnotify_destroy_mark().
+ */
+ BUG_ON(atomic_read(&entry->refcnt) < 1);
}

static bool audit_tree_send_event(struct fsnotify_group *group, struct inode *inode,
--
1.7.7


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