netdev - Re: [PATCH net] sctp: count sk_wmem_alloc by skb truesize in sctp_packet

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Date:   Tue, 20 Nov 2018 22:56:07 -0200
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     lucien.xin@...il.com, netdev@...r.kernel.org,
        linux-sctp@...r.kernel.org, nhorman@...driver.com
Subject: Re: [PATCH net] sctp: count sk_wmem_alloc by skb truesize in
 sctp_packet_transmit

On Mon, Nov 19, 2018 at 12:39:55PM -0800, David Miller wrote:
> From: Xin Long <lucien.xin@...il.com>
> Date: Sun, 18 Nov 2018 15:07:38 +0800
> 
> > Now sctp increases sk_wmem_alloc by 1 when doing set_owner_w for the
> > skb allocked in sctp_packet_transmit and decreases by 1 when freeing
> > this skb.
> > 
> > But when this skb goes through networking stack, some subcomponents
> > might change skb->truesize and add the same amount on sk_wmem_alloc.
> > However sctp doesn't know the amount to decrease by, it would cause
> > a leak on sk->sk_wmem_alloc and the sock can never be freed.
> > 
> > Xiumei found this issue when it hit esp_output_head() by using sctp
> > over ipsec, where skb->truesize is added and so is sk->sk_wmem_alloc.
> > 
> > Since sctp has used sk_wmem_queued to count for writable space since
> > Commit cd305c74b0f8 ("sctp: use sk_wmem_queued to check for writable
> > space"), it's ok to fix it by counting sk_wmem_alloc by skb truesize
> > in sctp_packet_transmit.
> > 
> > Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
> > Reported-by: Xiumei Mu <xmu@...hat.com>
> > Signed-off-by: Xin Long <lucien.xin@...il.com>
> 
> Applied and queued up for -stable.

Dave, is there a way that we can check to which versions you queued it
up?

Asking because even though this patch fixes cac2661c53f3 (v4.10) and
the patch probably applies cleanly, it has a dependency on
cd305c74b0f8 (v4.19) and fixing the issue in older kernels either need
a different fix or backport of cd305c74b0f8 too.