netdev - Re: [PATCH bpf v2] bpf: fix memory leak in lpm_trie map

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Date:   Wed, 21 Feb 2018 19:40:14 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Yonghong Song <yhs@...com>
Cc:     ast@...com, daniel@...earbox.net, netdev@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH bpf v2] bpf: fix memory leak in lpm_trie map_free
 callback function

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@...ian.org>
> > Reported-by: Alexei Starovoitov <ast@...nel.org>
> > Tested-by: Mathieu Malaterre <malat@...ian.org>
> > Signed-off-by: Yonghong Song <yhs@...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