netdev - Re: [bpf-next PATCH] bpf: sockmap, fix skmsg recvmsg handler to track size correctly

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Message-ID: <20181016222743.yrlouu57hicsxqik@ast-mbp.dhcp.thefacebook.com>
Date:   Tue, 16 Oct 2018 15:27:44 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org
Subject: Re: [bpf-next PATCH] bpf: sockmap, fix skmsg recvmsg handler to
 track size correctly

On Tue, Oct 16, 2018 at 10:36:01AM -0700, John Fastabend wrote:
> When converting sockmap to new skmsg generic data structures we missed
> that the recvmsg handler did not correctly use sg.size and instead was
> using individual elements length. The result is if a sock is closed
> with outstanding data we omit the call to sk_mem_uncharge() and can
> get the warning below.
> 
> [   66.728282] WARNING: CPU: 6 PID: 5783 at net/core/stream.c:206 sk_stream_kill_queues+0x1fa/0x210
> 
> To fix this correct the redirect handler to xfer the size along with
> the scatterlist and also decrement the size from the recvmsg handler.
> Now when a sock is closed the remaining 'size' will be decremented
> with sk_mem_uncharge().
> 
> Signed-off-by: John Fastabend <john.fastabend@...il.com>

Acked-by: Alexei Starovoitov <ast@...nel.org>