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Patch "staging: comedi: das1800: fix possible NULL dereference" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message May 30, 2016

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This is a note to let you know that I've just added the patch titled

staging: comedi: das1800: fix possible NULL dereference

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
staging-comedi-das1800-fix-possible-null-dereference.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From d375278d666760e195693b57415ba0a125cadd55 Mon Sep 17 00:00:00 2001

From: H Hartley Sweeten <[email protected]>
Date: Fri, 8 Apr 2016 10:14:58 -0700
Subject: staging: comedi: das1800: fix possible NULL dereference

From: H Hartley Sweeten <[email protected]>

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 <[email protected]>
Reviewed-by Ian Abbott <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/staging/comedi/drivers/das1800.c |   22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)
drivers/staging/comedi/drivers/das1800.c +13 -9
@@ -567,14 +567,17 @@ static int das1800_cancel(struct comedi_
 	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
 {
 	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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/staging-comedi-das1800-fix-possible-null-dereference.patch