linux-kernel - Re: [PATCH] tty: Fix unreasonable write toward closed pty.

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Message-ID: <50D217B4.6000104@ilyx.ru>
Date:	Wed, 19 Dec 2012 23:38:28 +0400
From:	Ilya Zykov <ilya@...x.ru>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Cox <alan@...ux.intel.com>, Jiri Slaby <jslaby@...e.cz>,
	Peter Hurley <peter@...leysoftware.com>,
	Sasha Levin <levinsasha928@...il.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: Fix unreasonable write toward closed pty.

On 19.12.2012 23:10, Alan Cox wrote:
>> diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
>> index a82b399..1ce1362 100644
>> --- a/drivers/tty/pty.c
>> +++ b/drivers/tty/pty.c
>> @@ -116,6 +116,8 @@ static int pty_space(struct tty_struct *to)
>>  
>>  static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
>>  {
>> +	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
>> +		return -EIO;
> 
> The flag can change between the test and ny further code being executed ?
> 
> Alan
> 

Yes, if I understand you correctly, but this is no matter here,
because ldisc's layer will wait, flush this data later.
Here, only beginning stage of tty_close.
This is safe later stage from unnecessary data.

Ilya

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