Re: [PATCH bpf v2] bpf: fix memory leak in lpm_trie map_free callback function

[Yonghong Song <yhs@fb.com>]

On 2/21/18 7:40 PM, Eric Dumazet wrote:
> On Tue, 2018-02-13 at 19:17 -0800, Alexei Starovoitov wrote:
>> On Tue, Feb 13, 2018 at 07:00:21PM -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 <malat@debian.org>
>>> Reported-by: Alexei Starovoitov <ast@kernel.org>
>>> Tested-by: Mathieu Malaterre <malat@debian.org>
>>> Signed-off-by: Yonghong Song <yhs@fb.com>
>>> ---
>>>   kernel/bpf/lpm_trie.c | 11 +++++++----
>>>   1 file changed, 7 insertions(+), 4 deletions(-)
>>>
>>> v1->v2:
>>>    Make comments more precise and make label name more appropriate,
>>>    as suggested by Daniel
>>
>> Applied to bpf tree, Thanks Yonghong.
> 
> 
> This does not look good.
> 
> LOCKDEP surely should complain to
> 
> node = rcu_dereference_protected(*slot, lockdep_is_held(&trie->lock));
> 
> Since we no longer hold trie->lock

Eric,

Thanks for spotting this issue. Will fix this issue soon.

Yonghong