[PATCH 4.2.y-ckt 036/206] staging: comedi: das1800: fix possible NULL dereference
From: Kamal Mostafa <hidden>
Date: 2016-06-09 22:11:30
Also in:
lkml
Subsystem:
staging subsystem, the rest · Maintainers:
Greg Kroah-Hartman, Linus Torvalds
4.2.8-ckt12 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: H Hartley Sweeten <hsweeten@visionengravers.com>
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 <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <redacted>
---
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