linux-kernel - Re: [linus:master] [serial] 43066e3222: BUG:kernel_NULL_pointer

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Date: Fri, 5 Apr 2024 08:46:17 +0300
From: Tony Lindgren <tony@...mide.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: kernel test robot <oliver.sang@...el.com>,
	Yicong Yang <yangyicong@...ilicon.com>, oe-lkp@...ts.linux.dev,
	lkp@...el.com, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable <stable@...nel.org>, linux-serial@...r.kernel.org
Subject: Re: [linus:master] [serial]  43066e3222:
 BUG:kernel_NULL_pointer_dereference,address

* Andy Shevchenko <andriy.shevchenko@...ux.intel.com> [240404 14:34]:
> On Thu, Apr 04, 2024 at 09:54:15AM +0300, Tony Lindgren wrote:
> > * Andy Shevchenko <andriy.shevchenko@...ux.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]);
> > 
> > Maybe we can set UPF_DEAD a bit earlier as below?
> 
> We should do this under port_mutex. Otherwise we replace one race by another.

Oh right.. And adding some better check in addition to UPF_DEAD
would be better.

Regards,

Tony