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From: Jiri Olsa <jolsa@redhat.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Alan Cox <alan@linux.intel.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Kay Sievers <kay.sievers@vrfy.org>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	Arnd Bergmann <arnd@arndb.de>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: BUG: NULL pointer deref in tty port / uart
Date: Wed, 18 May 2011 16:44:29 +0200	[thread overview]
Message-ID: <20110518144429.GC2011@jolsa.brq.redhat.com> (raw)
In-Reply-To: <20110518153636.5cdcdd78@lxorguk.ukuu.org.uk>

On Wed, May 18, 2011 at 03:36:36PM +0100, Alan Cox wrote:
> > have the same issue.. looks like we should not NULL the port->tty
> > if there's blocked open, but not sure what's exactly the logic
> > behind "port's block_open and count" ..
> 
> A pending open is not a user of the tty as far as the rest of the stack
> is concerned. I also don't see why clearing port->tty is causing this
> crash because nothing on that path should ever be going via port->tty and
> it isn't safe to do so.
> 
> > attached patch fixes it for me
> 
> But still breaks on hangup where we can't do that.
> 
> Where is port->tty getting misused to cause the crash, that is the bit
> I'm missing somewhere.

I think it's the 

uart_update_termios in uart_dtr_rts (drivers/tty/serial/serial_core.c)

called path:

tty_port_block_til_ready
	tty_port_raise_dtr_rts
		uart_dtr_rts
			uart_update_termios

jirka

  reply	other threads:[~2011-05-18 14:44 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-17 23:12 BUG: NULL pointer deref in tty port / uart Frederic Weisbecker
2011-05-17 23:44 ` Alan Cox
2011-05-18 14:26   ` Jiri Olsa
2011-05-18 14:36     ` Alan Cox
2011-05-18 14:44       ` Jiri Olsa [this message]
2011-05-18 14:50         ` Alan Cox
2011-05-18 19:42           ` Greg KH
2011-05-19 11:19             ` Jiri Olsa
2011-05-19 12:51               ` Greg KH
2011-05-19 13:58                 ` Jiri Olsa
2011-05-19 14:07                   ` Frederic Weisbecker

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