[PATCH 08/14] audit: Provide helper for dropping mark's chunk reference

Jan Kara
2018-10-17T10:14:59Z

Provide a helper function audit_mark_put_chunk() for dropping mark's
reference (which has to happen only after RCU grace period expires).
Currently that happens only from a single place but in later patches we
introduce more callers.

Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
kernel/audit_tree.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index d150514ff15e..35c031ebcc12 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -132,10 +132,20 @@ static void __put_chunk(struct rcu_head *rcu)
audit_put_chunk(chunk);
}

+/*
+ * Drop reference to the chunk that was held by the mark. This is the reference
+ * that gets dropped after we've removed the chunk from the hash table and we
+ * use it to make sure chunk cannot be freed before RCU grace period expires.
+ */
+static void audit_mark_put_chunk(struct audit_chunk *chunk)
+{
+ call_rcu(&chunk->head, __put_chunk);
+}
+
static void audit_tree_destroy_watch(struct fsnotify_mark *entry)
{
struct audit_chunk *chunk = container_of(entry, struct audit_chunk, mark);
- call_rcu(&chunk->head, __put_chunk);
+ audit_mark_put_chunk(chunk);
}

static struct audit_chunk *alloc_chunk(int count)
--
2.16.4