On Mon, 2018-02-12 at 13:58 -0800, Yonghong Song wrote:
> There is a memory leak happening in lpm_trie map_free callback
> function trie_free. The trie structure itself does not get freed.
>
> Also, trie_free function did not do synchronize_rcu before freeing
> various data structures. This is incorrect as some rcu_read_lock
> region(s) for lookup, update, delete or get_next_key may not complete yet.
> The fix is to add synchronize_rcu in the beginning of trie_free.
> The useless spin_lock is removed from this function as well.
>
> Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map
> implementation")
> Reported-by: Mathieu Malaterre <[email protected]>
> Reported-by: Alexei Starovoitov <[email protected]>
> Tested-by: Mathieu Malaterre <[email protected]>
> Signed-off-by: Yonghong Song <[email protected]>
> ---
> kernel/bpf/lpm_trie.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
> index 7b469d1..9b41ea4 100644
> --- a/kernel/bpf/lpm_trie.c
> +++ b/kernel/bpf/lpm_trie.c
> @@ -555,7 +555,12 @@ static void trie_free(struct bpf_map *map)
> struct lpm_trie_node __rcu **slot;
> struct lpm_trie_node *node;
>
> - raw_spin_lock(&trie->lock);
> + /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
> + * so the programs (can be more than one that used this map) were
> + * disconnected from events. Wait for outstanding programs to complete
> + * update/lookup/delete/get_next_key and free the trie.
> + */
> + synchronize_rcu();
>
Please do not do that.
Use kfree_rcu() instead (adding one struct rcu_head in struct lpm_trie)
> /* Always start at the root and walk down to a node that has no
> * children. Then free that node, nullify its reference in the parent
> @@ -588,7 +593,7 @@ static void trie_free(struct bpf_map *map)
> }
>
> unlock:
> - raw_spin_unlock(&trie->lock);
> + kfree(trie);
> }
>
> static int trie_get_next_key(struct bpf_map *map, void *_key, void
> *_next_key)
