[PATCH 11/14] audit: Drop all unused chunk nodes during deletion

[Richard Guy Briggs]

On 2018-10-17 12:15, Jan Kara wrote:
> When deleting chunk from a tree, drop all unused nodes in a chunk
> instead of just the one used by the tree. This gets rid of possibly
> lingering unused nodes (created due to fallback path in untag_chunk())
> and also removes some special cases and will allow us to simplify
> locking in untag_chunk().

Reviewed-by: Richard Guy Briggs <rgb at redhat.com>

> Signed-off-by: Jan Kara <jack at suse.cz>
> ---
>  kernel/audit_tree.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index ca2b6baff7aa..145e8c92dd31 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -277,8 +277,7 @@ static struct audit_chunk *find_chunk(struct node *p)
>  	return container_of(p, struct audit_chunk, owners[0]);
>  }
>  
> -static void replace_chunk(struct audit_chunk *new, struct audit_chunk *old,
> -			  struct node *skip)
> +static void replace_chunk(struct audit_chunk *new, struct audit_chunk *old)
>  {
>  	struct audit_tree *owner;
>  	int i, j;
> @@ -288,7 +287,7 @@ static void replace_chunk(struct audit_chunk *new, struct audit_chunk *old,
>  	list_for_each_entry(owner, &new->trees, same_root)
>  		owner->root = new;
>  	for (i = j = 0; j < old->count; i++, j++) {
> -		if (&old->owners[j] == skip) {
> +		if (!old->owners[j].owner) {
>  			i--;
>  			continue;
>  		}
> @@ -322,20 +321,28 @@ static void remove_chunk_node(struct audit_chunk *chunk, struct node *p)
>  	put_tree(owner);
>  }
>  
> +static int chunk_count_trees(struct audit_chunk *chunk)
> +{
> +	int i;
> +	int ret = 0;
> +
> +	for (i = 0; i < chunk->count; i++)
> +		if (chunk->owners[i].owner)
> +			ret++;
> +	return ret;
> +}
> +
>  static void untag_chunk(struct node *p)
>  {
>  	struct audit_chunk *chunk = find_chunk(p);
>  	struct fsnotify_mark *entry = chunk->mark;
>  	struct audit_chunk *new = NULL;
> -	int size = chunk->count - 1;
> +	int size;
>  
>  	remove_chunk_node(chunk, p);
>  	fsnotify_get_mark(entry);
>  	spin_unlock(&hash_lock);
>  
> -	if (size)
> -		new = alloc_chunk(size);
> -
>  	mutex_lock(&entry->group->mark_mutex);
>  	/*
>  	 * mark_mutex protects mark from getting detached and thus also from
> @@ -348,6 +355,7 @@ static void untag_chunk(struct node *p)
>  		goto out;
>  	}
>  
> +	size = chunk_count_trees(chunk);
>  	if (!size) {
>  		chunk->dead = 1;
>  		spin_lock(&hash_lock);
> @@ -360,6 +368,7 @@ static void untag_chunk(struct node *p)
>  		goto out;
>  	}
>  
> +	new = alloc_chunk(size);
>  	if (!new)
>  		goto out_mutex;
>  
> @@ -375,7 +384,7 @@ static void untag_chunk(struct node *p)
>  	 * This has to go last when updating chunk as once replace_chunk() is
>  	 * called, new RCU readers can see the new chunk.
>  	 */
> -	replace_chunk(new, chunk, p);
> +	replace_chunk(new, chunk);
>  	spin_unlock(&hash_lock);
>  	fsnotify_detach_mark(entry);
>  	mutex_unlock(&entry->group->mark_mutex);
> @@ -520,7 +529,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
>  	 * This has to go last when updating chunk as once replace_chunk() is
>  	 * called, new RCU readers can see the new chunk.
>  	 */
> -	replace_chunk(chunk, old, NULL);
> +	replace_chunk(chunk, old);
>  	spin_unlock(&hash_lock);
>  	fsnotify_detach_mark(old_entry);
>  	mutex_unlock(&audit_tree_group->mark_mutex);
> -- 
> 2.16.4
> 

- RGB

--
Richard Guy Briggs <rgb at redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635