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Date: Thu, 19 May 2011 05:51:20 -0700
From: Greg KH <gregkh@suse.de>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Alan Cox <alan@linux.intel.com>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Kay Sievers <kay.sievers@vrfy.org>, Arnd Bergmann <arnd@arndb.de>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: BUG: NULL pointer deref in tty port / uart
Message-ID: <20110519125120.GA12844@suse.de>
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On Thu, May 19, 2011 at 01:19:01PM +0200, Jiri Olsa wrote:
> On Wed, May 18, 2011 at 12:42:12PM -0700, Greg KH wrote:
> > On Wed, May 18, 2011 at 03:50:33PM +0100, Alan Cox wrote:
> > > > 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
> > > 
> > > Ah that would explain why I can't find and dup it - it isn't found in
> > > the current -next tree.
> > > 
> > > 
> > > c7d7abff40c27f82fe78b1091ab3fad69b2546f9 (and thereafter)
> > > 
> > > Jiri Slaby fixed it in sorting out uart_startup
> > > 
> > > I guess these should now get tagged for -stable.
> > 
> > So that would be the following patches in the linux-next tree:
> > 	c7d7abff40c27f82fe78b1091ab3fad69b2546f9 serial: core, move termios handling to uart_startup
> > 	303a7a1199c20f7c9452f024a6e17bf348b6b398 serial: core, do not set DTR/RTS twice on startup
> > 	6f5c24ad0f7619502199185a026a228174a27e68 serial: core, remove uart_update_termios
> > 
> > right?
> > 
> > Anything else need to be backported?
> > 
> > Frederic, can you test that these 3 patches solve the problem for you?
> > If you want, I can send them to you separately if you don't have a copy
> > of linux-next around anywhere.
> > 
> > thanks,
> > 
> > greg k-h
> 
> I tried linux-next and cannot hit the issue anymore

That's great, but can you try .38 or .39 with those patches above and
verify that they solve the problem?

thanks,

greg k-h