lkml.org 
[lkml]   [2014]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] spi/pxa2xx: Clear cur_chip pointer before starting next message
On Thu, Dec 04, 2014 at 10:01:06PM +0100, Robert Jarzmik wrote:
> Mika Westerberg <mika.westerberg@linux.intel.com> writes:
>
> > Once the current message is finished, the driver notifies SPI core about
> > this by calling spi_finalize_current_message(). This function queues next
> > message to be transferred. If there are more messages in the queue, it is
> > possible that the driver is asked to transfer the next message at this
> > point.
> >
> > When spi_finalize_current_message() returns the driver clears the
> > drv_data->cur_chip pointer to NULL. The problem is that if the driver
> > already started the next message clearing drv_data->cur_chip will cause
> > NULL pointer dereference which crashes the kernel like:
> ..zip..
> > Fix this by clearing drv_data->cur_chip before we call
> > spi_finalize_current_message().
>
> So with your change, we have :
> drv_data->cur_chip = NULL;
> spi_finalize_current_message(drv_data->master);
>
> In that case, if spi_finalize_current_message() queues another message, upon
> this next message completion, won't giveback() be called, and dereference
> cur_chip as well ?

When the next message is started pxa2xx_spi_transfer_one_message() gets
called and that will set cur_chip again.


\
 
 \ /
  Last update: 2014-12-05 10:01    [W:0.057 / U:1.080 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site