[PATCH 06/22] audit: Abstract hash key handling

[Paul Moore]

On Thu, Dec 22, 2016 at 4:15 AM, Jan Kara <jack at suse.cz> wrote:
> Audit tree currently uses inode pointer as a key into the hash table.
> Getting that from notification mark will be somewhat more difficult with
> coming fsnotify changes and there's no reason we really have to use the
> inode pointer. So abstract getting of hash key from the audit chunk and
> inode so that we can switch to a different key easily later.
>
> CC: Paul Moore <paul at paul-moore.com>
> Signed-off-by: Jan Kara <jack at suse.cz>
> ---
>  kernel/audit_tree.c | 39 ++++++++++++++++++++++++++++-----------
>  1 file changed, 28 insertions(+), 11 deletions(-)

I have no objections with this patch in particular, but in patch 8,
are you certain that inode_to_key() and chunk_to_key() will continue
to return the same key value?

> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index 156b6a93f4fc..f0859828de09 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -163,33 +163,48 @@ enum {HASH_SIZE = 128};
>  static struct list_head chunk_hash_heads[HASH_SIZE];
>  static __cacheline_aligned_in_smp DEFINE_SPINLOCK(hash_lock);
>
> -static inline struct list_head *chunk_hash(const struct inode *inode)
> +/* Function to return search key in our hash from inode. */
> +static unsigned long inode_to_key(const struct inode *inode)
>  {
> -       unsigned long n = (unsigned long)inode / L1_CACHE_BYTES;
> +       return (unsigned long)inode;
> +}
> +
> +/*
> + * Function to return search key in our hash from chunk. Key 0 is special and
> + * should never be present in the hash.
> + */
> +static unsigned long chunk_to_key(struct audit_chunk *chunk)
> +{
> +       return (unsigned long)chunk->mark.inode;
> +}
> +
> +static inline struct list_head *chunk_hash(unsigned long key)
> +{
> +       unsigned long n = key / L1_CACHE_BYTES;
>         return chunk_hash_heads + n % HASH_SIZE;
>  }
>
>  /* hash_lock & entry->lock is held by caller */
>  static void insert_hash(struct audit_chunk *chunk)
>  {
> -       struct fsnotify_mark *entry = &chunk->mark;
> +       unsigned long key = chunk_to_key(chunk);
>         struct list_head *list;
>
> -       if (!entry->inode)
> +       if (!key)
>                 return;
> -       list = chunk_hash(entry->inode);
> +       list = chunk_hash(key);
>         list_add_rcu(&chunk->hash, list);
>  }
>
>  /* called under rcu_read_lock */
>  struct audit_chunk *audit_tree_lookup(const struct inode *inode)
>  {
> -       struct list_head *list = chunk_hash(inode);
> +       unsigned long key = inode_to_key(inode);
> +       struct list_head *list = chunk_hash(key);
>         struct audit_chunk *p;
>
>         list_for_each_entry_rcu(p, list, hash) {
> -               /* mark.inode may have gone NULL, but who cares? */
> -               if (p->mark.inode == inode) {
> +               if (chunk_to_key(p) == key) {
>                         atomic_long_inc(&p->refs);
>                         return p;
>                 }
> @@ -585,7 +600,8 @@ int audit_remove_tree_rule(struct audit_krule *rule)
>
>  static int compare_root(struct vfsmount *mnt, void *arg)
>  {
> -       return d_backing_inode(mnt->mnt_root) == arg;
> +       return inode_to_key(d_backing_inode(mnt->mnt_root)) ==
> +              (unsigned long)arg;
>  }
>
>  void audit_trim_trees(void)
> @@ -620,9 +636,10 @@ void audit_trim_trees(void)
>                 list_for_each_entry(node, &tree->chunks, list) {
>                         struct audit_chunk *chunk = find_chunk(node);
>                         /* this could be NULL if the watch is dying else where... */
> -                       struct inode *inode = chunk->mark.inode;
>                         node->index |= 1U<<31;
> -                       if (iterate_mounts(compare_root, inode, root_mnt))
> +                       if (iterate_mounts(compare_root,
> +                                          (void *)chunk_to_key(chunk),
> +                                          root_mnt))
>                                 node->index &= ~(1U<<31);
>                 }
>                 spin_unlock(&hash_lock);
> --
> 2.10.2
>



-- 
paul moore
www.paul-moore.com