linux-kernel - Re: [PATCH] serial: rp2: disable interrupt in rp2

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Date:   Thu, 20 May 2021 16:30:05 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Zheyu Ma <zheyuma97@...il.com>
Cc:     cernekee@...il.com, jirislaby@...nel.org,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: rp2: disable interrupt in rp2_probe():

On Fri, May 14, 2021 at 11:17:07AM +0000, Zheyu Ma wrote:
> In 'rp2_probe', the driver registers 'rp2_uart_interrupt' then calls
> 'rp2_fw_cb' through 'request_firmware_nowait'. In 'rp2_fw_cb', if the
> firmware don't exists, function just return without initializing ports
> of 'rp2_card'. But now the interrupt handler function has been registered,
> and when an interrupt comes('rp2' may shares an interrupt line with other
> devices), 'rp2_uart_interrupt' may access those ports then causing NULL
> pointer dereference or other bugs.
> 
> Fix this by disabling interrupt after registering 'rp2_uart_interrupt',
> and enable it in 'rp2_uart_startup'.

What prevents an interrupt from coming in right after callin
rp2_uart_interrupt()?  The driver has to be able to handle that.  Why is
the interrupt being registered before the firmware is loaded?  That
should be the proper fix as once you register an interrupt, the driver
HAS to be able to properly handle it.

thanks,

greg k-h