linux-kernel - Re: buffer overflows in the tty flip buffer in 2.6.17

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Message-ID: <20070217151729.GS7584@csclub.uwaterloo.ca>
Date:	Sat, 17 Feb 2007 10:17:29 -0500
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	Mockern <Mockern@...dex.ru>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: buffer overflows in the tty flip buffer in 2.6.17

On Sat, Feb 17, 2007 at 03:29:31PM +0300, Mockern wrote:
> When data is received from the hardware, it needs to be placed into the tty device's flip buffer. This can be done with the following bit of code:
> 
> for (i = 0; i < data_size; ++i) {
>         if (tty->flip.count >= TTY_FLIPBUF_SIZE)
>                 tty_flip_buffer_push(tty);
>         tty_insert_flip_char(tty, data[i], 0);
> }
> tty_flip_buffer_push(tty);
> 
> This example makes sure there are no buffer overflows in the tty flip buffer as the data is being added. 
> 
> But how it is done in 2.6.17 linux kernel? I did check this "overflow code" in new tty driver's code. This code looks like just removed. But somehow overflow in the tty buffer must be kept.

Well there was a problem in 2.6.16, which was fixed by 2.6.18, although
I am not sure if it was done by 2.6.17.  It would loose characters due
to buffer overflow and not properly checking under high load.  I grabbed
a few patches from the git tree that were added after 2.6.16 to fix the
tty problems I was having.

--
Len Sorensen
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