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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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