Messages in this thread |  | | From | Willem de Bruijn <> | Date | Sun, 9 Aug 2020 11:12:33 +0200 | Subject | Re: [PATCH net] drivers/net/wan/x25_asy: Added needed_headroom and a skb->len check |
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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?
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