From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932850AbcFIWLa (ORCPT ); Thu, 9 Jun 2016 18:11:30 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:50728 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932329AbcFIVRu (ORCPT ); Thu, 9 Jun 2016 17:17:50 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: H Hartley Sweeten , Greg Kroah-Hartman , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 036/206] staging: comedi: das1800: fix possible NULL dereference Date: Thu, 9 Jun 2016 14:14:05 -0700 Message-Id: <1465507015-23052-37-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1465507015-23052-1-git-send-email-kamal@canonical.com> References: <1465507015-23052-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.2.8-ckt12 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: H Hartley Sweeten commit d375278d666760e195693b57415ba0a125cadd55 upstream. DMA is optional with this driver. If it was not enabled the devpriv->dma pointer will be NULL. Fix the possible NULL pointer dereference when trying to disable the DMA channels in das1800_ai_cancel() and tidy up the comments to fix the checkpatch.pl issues: WARNING: line over 80 characters It's probably harmless in das1800_ai_setup_dma() because the 'desc' pointer will not be used if DMA is disabled but fix it there also. Fixes: 99dfc3357e98 ("staging: comedi: das1800: remove depends on ISA_DMA_API limitation") Signed-off-by: H Hartley Sweeten Reviewed-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa --- drivers/staging/comedi/drivers/das1800.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/drivers/staging/comedi/drivers/das1800.c b/drivers/staging/comedi/drivers/das1800.c index 94078118..3be1096 100644 --- a/drivers/staging/comedi/drivers/das1800.c +++ b/drivers/staging/comedi/drivers/das1800.c @@ -567,14 +567,17 @@ static int das1800_cancel(struct comedi_device *dev, struct comedi_subdevice *s) struct comedi_isadma_desc *desc; int i; - outb(0x0, dev->iobase + DAS1800_STATUS); /* disable conversions */ - outb(0x0, dev->iobase + DAS1800_CONTROL_B); /* disable interrupts and dma */ - outb(0x0, dev->iobase + DAS1800_CONTROL_A); /* disable and clear fifo and stop triggering */ - - for (i = 0; i < 2; i++) { - desc = &dma->desc[i]; - if (desc->chan) - comedi_isadma_disable(desc->chan); + /* disable and stop conversions */ + outb(0x0, dev->iobase + DAS1800_STATUS); + outb(0x0, dev->iobase + DAS1800_CONTROL_B); + outb(0x0, dev->iobase + DAS1800_CONTROL_A); + + if (dma) { + for (i = 0; i < 2; i++) { + desc = &dma->desc[i]; + if (desc->chan) + comedi_isadma_disable(desc->chan); + } } return 0; @@ -934,13 +937,14 @@ static void das1800_ai_setup_dma(struct comedi_device *dev, { struct das1800_private *devpriv = dev->private; struct comedi_isadma *dma = devpriv->dma; - struct comedi_isadma_desc *desc = &dma->desc[0]; + struct comedi_isadma_desc *desc; unsigned int bytes; if ((devpriv->irq_dma_bits & DMA_ENABLED) == 0) return; dma->cur_dma = 0; + desc = &dma->desc[0]; /* determine a dma transfer size to fill buffer in 0.3 sec */ bytes = das1800_ai_transfer_size(dev, s, desc->maxsize, 300000000); -- 2.7.4