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

Richard Guy Briggs
2018-10-18T19:32:02Z

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@redhat.com>

> Signed-off-by: Jan Kara <jack@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@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