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audit: Simplify locking around untag_chunk()

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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: Jan Kara <jack@suse.cz>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Jan Kara 2018-11-12 09:54:56 -05:00 committed by Paul Moore
parent c22fcde775
commit 8432c70062
1 changed files with 40 additions and 37 deletions
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77
kernel/audit_tree.c
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@ -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(p);
untag_chunk(chunk, mark);
fsnotify_put_mark(mark);
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;
prune_tree_chunks(tree, true);
node = list_entry(tree->chunks.next, struct node, list);
/* 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);