netdev - Re: [tipc-discussion] [net v3 1/1] tipc: fix memory leak caused by tipc_buf

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Date:   Tue, 27 Oct 2020 13:50:23 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Tung Nguyen <tung.q.nguyen@...tech.com.au>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        tipc-discussion@...ts.sourceforge.net
Subject: Re: [tipc-discussion] [net v3 1/1] tipc: fix memory leak caused by tipc_buf_append()

On Tue, Oct 27, 2020 at 1:09 PM Tung Nguyen
<tung.q.nguyen@...tech.com.au> wrote:
>
> Commit ed42989eab57 ("tipc: fix the skb_unshare() in tipc_buf_append()")
> replaced skb_unshare() with skb_copy() to not reduce the data reference
> counter of the original skb intentionally. This is not the correct
> way to handle the cloned skb because it causes memory leak in 2
> following cases:
>  1/ Sending multicast messages via broadcast link
>   The original skb list is cloned to the local skb list for local
>   destination. After that, the data reference counter of each skb
>   in the original list has the value of 2. This causes each skb not
>   to be freed after receiving ACK:

This does not make sense at all.

skb_unclone() expects refcnt == 1, as stated in the comments
above pskb_expand_head(). skb_unclone() was used prior to
Xin Long's commit.

So either the above is wrong, or something important is still missing
in your changelog. None of them is addressed in your V3.

I also asked you two questions before you sent V3, you seem to
intentionally ignore them. This is not how we collaborate.

Thanks.