From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Xie He <xie.he.0141@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Network Development <netdev@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Linux X25 <linux-x25@vger.kernel.org>,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
Martin Schiller <ms@dev.tdt.de>
Subject: Re: [PATCH net] drivers/net/wan/x25_asy: Added needed_headroom and a skb->len check
Date: Sun, 9 Aug 2020 11:12:33 +0200 [thread overview]
Message-ID: <CA+FuTSe-FaQFn4WNvVPJ1v+jVZAghgd1AZc-cWn2+GjPR4GzVQ@mail.gmail.com> (raw)
In-Reply-To: <20200809023548.684217-1-xie.he.0141@gmail.com>
On Sun, Aug 9, 2020 at 4:36 AM Xie He <xie.he.0141@gmail.com> wrote:
>
> 1. Added a skb->len check
>
> This driver expects upper layers to include a pseudo header of 1 byte
> when passing down a skb for transmission. This driver will read this
> 1-byte header. This patch added a skb->len check before reading the
> header to make sure the header exists.
>
> 2. Added needed_headroom
>
> When this driver transmits data,
> first this driver will remove a pseudo header of 1 byte,
> then the lapb module will prepend the LAPB header of 2 or 3 bytes.
> So the value of needed_headroom in this driver should be 3 - 1.
>
> Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
> Cc: Martin Schiller <ms@dev.tdt.de>
> Signed-off-by: Xie He <xie.he.0141@gmail.com>
The patch is analogous to commit c7ca03c216ac
("drivers/net/wan/lapbether: Added needed_headroom and a skb->len
check").
Seems to make sense based on call stack
x25_asy_xmit // skb_pull(skb, 1)
lapb_data_request
lapb_kick
lapb_send_iframe // skb_push(skb, 2)
lapb_transmit_buffer // skb_push(skb, 1)
lapb_data_transmit
x25_asy_data_transmit
x25_asy_encaps
But I frankly don't know this code and would not modify logic that no
one has complained about for many years without evidence of a real
bug.
Were you able to actually exercise this path, similar to lapb_ether:
configure the device, send data from a packet socket? If so, can you
share the configuration steps?
next prev parent reply other threads:[~2020-08-09 9:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-09 2:35 [PATCH net] drivers/net/wan/x25_asy: Added needed_headroom and a skb->len check Xie He
2020-08-09 9:12 ` Willem de Bruijn [this message]
2020-08-09 18:08 ` Xie He
2020-08-10 7:20 ` Willem de Bruijn
2020-08-10 19:50 ` Xie He
2020-08-11 10:50 ` Willem de Bruijn
2020-08-12 2:26 ` Xie He
2020-08-11 17:32 ` David Miller
2020-08-12 2:30 ` Xie He
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