linux-kernel - Re: [Suggestion] drivers/tty: drivers/char/: for MAX_ASYNC_BUFFER

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Date:	Thu, 29 Nov 2012 13:57:59 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-serial@...r.kernel.org
Subject: Re: [Suggestion] drivers/tty: drivers/char/:  for MAX_ASYNC_BUFFER_SIZE

于 2012年11月29日 13:13, Greg KH 写道:
> On Thu, Nov 29, 2012 at 12:40:49PM +0800, Chen Gang wrote:
>> Hello Greg Kroah-Hartman:
>>
>> for MAX_ASYNC_BUFFER_SIZE:
>>   it is defined as 4096;
>>   but for the max buffer size which it processes, is 65535.
>>   so suggest to #define MAX_ASYNC_BUFFER_SIZE 0x10000  (better than 0xffff)
> 
> Please, send tty questions to the linux-serial@...r.kernel.org list
> also.

  I cc to linux-serial@...r.kernel.org, in this reply.

  I referenced the file MAINTAINERS, before sent original mail:

  it seems all drivers/tty/serial/* are relative with
linux-serial@...r.kernel.org. but our case is not relative
drivers/tty/serial. so for not bother them, I am not send to them,
originally.

  in MAINTAINERS, line 7438, I find for common of driver/tty/*, can send
to you and no cc, so I send you and cc to linux-kernel@...r.kernel.org.

  next time, for all tty questions, I will cc to
linux-serial@...r.kernel.org (not cc to linux-kernel@...r.kernel.org).

> 
> And, I really don't understand here, why do you want to change this?
> What is it going to change?  And why?
> 

Why:
  for the context MGSLPC_INFO *info in drivers/char/pcmcia/synclink_cs.c
    info->max_frame_size can be the value between 4096 .. 65535 (can be
set by its module input parameter)
    info->flag_buf length is 4096 (MAX_ASYNC_BUFFER_SIZE)
  in function rx_get_frame
    the framesize is limit by info->max_frame_size, but may still be
larger that 4096.
    when call function ldisc_receive_buf, info->flag_buf is equal to
4096, but framesize can be more than 4096. it will cause memory over flow.

What:
  #define MAX_ASYNC_BUFFER_SIZE  0x10000 (instead of 4096, originally).
  let it match the max frame size.

At last:
  my suggestion may be incorrect, need relative member (who expert about
it) to help checking.


  welcome another suggestion or completions.

  thanks.

gchen.

> greg k-h
> --
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> 


-- 
Chen Gang

Asianux Corporation
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