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Date:   Tue, 11 Aug 2020 16:02:51 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Kees Cook <keescook@...omium.org>, zhang.lin16@....com.cn,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: Fix potential memory leak in proto_register()

On Mon, Aug 10, 2020 at 5:19 AM Miaohe Lin <linmiaohe@...wei.com> wrote:
>
> If we failed to assign proto idx, we free the twsk_slab_name but forget to
> free the twsk_slab. Add a helper function tw_prot_cleanup() to free these
> together and also use this helper function in proto_unregister().
>
> Fixes: b45ce32135d1 ("sock: fix potential memory leak in proto_register()")
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  net/core/sock.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 49cd5ffe673e..c9083ad44ea1 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -3406,6 +3406,16 @@ static void sock_inuse_add(struct net *net, int val)
>  }
>  #endif
>
> +static void tw_prot_cleanup(struct timewait_sock_ops *twsk_prot)
> +{
> +       if (!twsk_prot)
> +               return;
> +       kfree(twsk_prot->twsk_slab_name);
> +       twsk_prot->twsk_slab_name = NULL;
> +       kmem_cache_destroy(twsk_prot->twsk_slab);

Hmm, are you sure you can free the kmem cache name before
kmem_cache_destroy()? To me, it seems kmem_cache_destroy()
frees the name via slab_kmem_cache_release() via kfree_const().
With your patch, we have a double-free on the name?

Or am I missing anything?

Thanks.

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