From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Nikula Subject: Re: [PATCH] spi: spidev: fix possible NULL dereference Date: Fri, 11 Sep 2015 15:11:32 +0300 Message-ID: <55F2C4F4.3090704@linux.intel.com> References: <1441883893-20596-1-git-send-email-sudipm.mukherjee@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sudip Mukherjee , Mark Brown Return-path: In-Reply-To: <1441883893-20596-1-git-send-email-sudipm.mukherjee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Hi On 09/10/2015 02:18 PM, Sudip Mukherjee wrote: > During the last close we are freeing spidev if spidev->spi is NULL, but > just before checking if spidev->spi is NULL we are dereferencing it. > Lets add a check there to avoid the NULL dereference. > > Signed-off-by: Sudip Mukherjee > --- > drivers/spi/spidev.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c > index fba92a5..ef008e5 100644 > --- a/drivers/spi/spidev.c > +++ b/drivers/spi/spidev.c > @@ -651,7 +651,8 @@ static int spidev_release(struct inode *inode, struct file *filp) > kfree(spidev->rx_buffer); > spidev->rx_buffer = NULL; > > - spidev->speed_hz = spidev->spi->max_speed_hz; > + if (spidev->spi) > + spidev->speed_hz = spidev->spi->max_speed_hz; > > /* ... after we unbound from the underlying device? */ > spin_lock_irq(&spidev->spi_lock); Actually this fixes a *real* NULL dereference case but it is not related to normal open/close life cycle of spidev. It requires that spidev is kept open when SPI master is removed. spidev->spi is set to NULL in spidev_remove() and it is called before spidev_release() in case master is removed while spidev is in use It would be good to update this to commit log, add a tag below and Cc Fixes: 9169051617df ("spi: spidev: Don't mangle max_speed_hz in underlying spi device") You can add these too: Reviewed-by: Jarkko Nikula Tested-by: Jarkko Nikula -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html