Commit 8432c700 authored by Jan Kara's avatar Jan Kara Committed by Paul Moore
Browse files

audit: Simplify locking around untag_chunk() 



untag_chunk() has to be called with hash_lock, it drops it and
reacquires it when returning. The unlocking of hash_lock is thus hidden
from the callers of untag_chunk() with is rather error prone. Reorganize
the code so that untag_chunk() is called without hash_lock, only with
mark reference preventing the chunk from going away.

Since this requires some more code in the caller of untag_chunk() to
assure forward progress, factor out loop pruning tree from all chunks
into a common helper function.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarRichard Guy Briggs <rgb@redhat.com>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent c22fcde7

kernel/audit_tree.c

+40 −37
Original line number Diff line number Diff line
@@ -332,28 +332,18 @@ static int chunk_count_trees(struct audit_chunk *chunk) 
	return ret;

}



static void untag_chunk(struct node *p)

static void untag_chunk(struct audit_chunk *chunk, struct fsnotify_mark *entry)

{

	struct audit_chunk *chunk = find_chunk(p);

	struct fsnotify_mark *entry = chunk->mark;

	struct audit_chunk *new = NULL;

	struct audit_chunk *new;

	int size;



	remove_chunk_node(chunk, p);

	fsnotify_get_mark(entry);

	spin_unlock(&hash_lock);



	mutex_lock(&entry->group->mark_mutex);

	mutex_lock(&audit_tree_group->mark_mutex);

	/*

	 * mark_mutex protects mark from getting detached and thus also from

	 * mark->connector->obj getting NULL.

	 */

	if (chunk->dead || !(entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {

		mutex_unlock(&entry->group->mark_mutex);

		if (new)

			fsnotify_put_mark(new->mark);

		goto out;

	}

	if (chunk->dead || !(entry->flags & FSNOTIFY_MARK_FLAG_ATTACHED))

		goto out_mutex;



	size = chunk_count_trees(chunk);

	if (!size) {
@@ -363,9 +353,9 @@ static void untag_chunk(struct node *p) 
		list_del_rcu(&chunk->hash);

		spin_unlock(&hash_lock);

		fsnotify_detach_mark(entry);

		mutex_unlock(&entry->group->mark_mutex);

		mutex_unlock(&audit_tree_group->mark_mutex);

		fsnotify_free_mark(entry);

		goto out;

		return;

	}



	new = alloc_chunk(size);
@@ -387,16 +377,13 @@ static void untag_chunk(struct node *p) 
	replace_chunk(new, chunk);

	spin_unlock(&hash_lock);

	fsnotify_detach_mark(entry);

	mutex_unlock(&entry->group->mark_mutex);

	mutex_unlock(&audit_tree_group->mark_mutex);

	fsnotify_free_mark(entry);

	fsnotify_put_mark(new->mark);	/* drop initial reference */

	goto out;

	return;



out_mutex:

	mutex_unlock(&entry->group->mark_mutex);

out:

	fsnotify_put_mark(entry);

	spin_lock(&hash_lock);

	mutex_unlock(&audit_tree_group->mark_mutex);

}



/* Call with group->mark_mutex held, releases it */
@@ -579,22 +566,45 @@ static void kill_rules(struct audit_tree *tree) 
}



/*

 * finish killing struct audit_tree

 * Remove tree from chunks. If 'tagged' is set, remove tree only from tagged

 * chunks. The function expects tagged chunks are all at the beginning of the

 * chunks list.

 */

static void prune_one(struct audit_tree *victim)

static void prune_tree_chunks(struct audit_tree *victim, bool tagged)

{

	spin_lock(&hash_lock);

	while (!list_empty(&victim->chunks)) {

		struct node *p;

		struct audit_chunk *chunk;

		struct fsnotify_mark *mark;



		p = list_entry(victim->chunks.next, struct node, list);

		p = list_first_entry(&victim->chunks, struct node, list);

		/* have we run out of marked? */

		if (tagged && !(p->index & (1U<<31)))

			break;

		chunk = find_chunk(p);

		mark = chunk->mark;

		remove_chunk_node(chunk, p);

		fsnotify_get_mark(mark);

		spin_unlock(&hash_lock);



		untag_chunk(chunk, mark);

		fsnotify_put_mark(mark);



		untag_chunk(p);

		spin_lock(&hash_lock);

	}

	spin_unlock(&hash_lock);

	put_tree(victim);

}



/*

 * finish killing struct audit_tree

 */

static void prune_one(struct audit_tree *victim)

{

	prune_tree_chunks(victim, false);

}



/* trim the uncommitted chunks from tree */



static void trim_marked(struct audit_tree *tree)
@@ -614,18 +624,11 @@ static void trim_marked(struct audit_tree *tree) 
			list_add(p, &tree->chunks);

		}

	}

	spin_unlock(&hash_lock);



	while (!list_empty(&tree->chunks)) {

		struct node *node;



		node = list_entry(tree->chunks.next, struct node, list);

	prune_tree_chunks(tree, true);



		/* have we run out of marked? */

		if (!(node->index & (1U<<31)))

			break;



		untag_chunk(node);

	}

	spin_lock(&hash_lock);

	if (!tree->root && !tree->goner) {

		tree->goner = 1;

		spin_unlock(&hash_lock);

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