linux-kernel - Re: [PATCH v2 2/2] TTY: ntty, add one more sanity check

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Message-ID: <20110607164423.GA32575@kroah.com>
Date:	Tue, 7 Jun 2011 09:44:23 -0700
From:	Greg KH <greg@...ah.com>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	gregkh@...e.de, jirislaby@...il.com, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v2 2/2] TTY: ntty, add one more sanity check

On Sun, Jun 05, 2011 at 02:16:17PM +0200, Jiri Slaby wrote:
> With the previous patch, we fixed another bug where read_buf was freed
> while we still was in n_tty_read. We currently check whether read_buf
> is NULL at the start of the function. Add one more check after we wake
> up from waiting for input.
> 
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
> ---
>  drivers/tty/n_tty.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
> index 95d0a9c..c62c856 100644
> --- a/drivers/tty/n_tty.c
> +++ b/drivers/tty/n_tty.c
> @@ -1785,6 +1785,7 @@ do_it_again:
>  				break;
>  			}
>  			timeout = schedule_timeout(timeout);
> +			BUG_ON(!tty->read_buf);

So, if we ever hit this, what are we going to do with this crash?

I really don't want to add more BUG_ON() calls to the kernel if at all
possible.  Or is it the case that we will crash if this case is true
soon afterward anyway?

thanks,

greg k-h
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