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Date: Thu, 4 Apr 2024 17:42:29 +0300
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Tony Lindgren <tony@atomide.com>
Cc: kernel test robot <oliver.sang@intel.com>,
	Yicong Yang <yangyicong@hisilicon.com>, oe-lkp@lists.linux.dev,
	lkp@intel.com, linux-kernel@vger.kernel.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable <stable@kernel.org>, linux-serial@vger.kernel.org
Subject: Re: [linus:master] [serial]  43066e3222:
 BUG:kernel_NULL_pointer_dereference,address
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On Thu, Apr 04, 2024 at 02:59:19PM +0300, Andy Shevchenko wrote:
> On Thu, Apr 04, 2024 at 09:54:15AM +0300, Tony Lindgren wrote:
> > * Andy Shevchenko <andriy.shevchenko@linux.intel.com> [240403 14:00]:
> > > Probably we need to check if the port is still open...
> > > 
> > > P.S. AFAIU the state / xmit is invalid pointer or so.
> > > 
> > > Culprit line:	serial_out(up, UART_TX, xmit->buf[xmit->tail]);
> 
> xmit.buf seems to be NULL, that's why this fails.
> 
> > Maybe we can set UPF_DEAD a bit earlier as below?
> 
> Lemme perform some tests later today.

Okay, so far it doesn't fix the issue AFAICT. The only reliable one right now
to me is clearing circ buffer before NULLifying it.

I'll send a formal patch.

-- 
With Best Regards,
Andy Shevchenko