[PATCH] spi: coldfire-qspi: Prevent NULL pointer dereference

[PATCH] spi: coldfire-qspi: Prevent NULL pointer dereference

[Axel Lin]

If pdata->cs_control is NULL, we will hit NULL pointer dereference in
mcfqspi_cs_select() and mcfqspi_cs_deselect(). Thus add NULL test for
pdata->cs_control in probe().

Signed-off-by: Axel Lin <axel.lin-8E1dMatC8ynQT0dZR+AlfA@public.gmane.org>
---
 drivers/spi/spi-coldfire-qspi.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-coldfire-qspi.c b/drivers/spi/spi-coldfire-qspi.c
index c29bbb0..b01616c 100644
--- a/drivers/spi/spi-coldfire-qspi.c
+++ b/drivers/spi/spi-coldfire-qspi.c
@@ -133,13 +133,13 @@ static void mcfqspi_cs_deselect(struct mcfqspi *mcfqspi, u8 chip_select,
 
 static int mcfqspi_cs_setup(struct mcfqspi *mcfqspi)
 {
-	return (mcfqspi->cs_control && mcfqspi->cs_control->setup) ?
+	return (mcfqspi->cs_control->setup) ?
 		mcfqspi->cs_control->setup(mcfqspi->cs_control) : 0;
 }
 
 static void mcfqspi_cs_teardown(struct mcfqspi *mcfqspi)
 {
-	if (mcfqspi->cs_control && mcfqspi->cs_control->teardown)
+	if (mcfqspi->cs_control->teardown)
 		mcfqspi->cs_control->teardown(mcfqspi->cs_control);
 }
 
@@ -366,6 +366,11 @@ static int mcfqspi_probe(struct platform_device *pdev)
 		return -ENOENT;
 	}
 
+	if (!pdata->cs_control) {
+		dev_dbg(&pdev->dev, "pdata->cs_control is NULL\n");
+		return -EINVAL;
+	}
+
 	master = spi_alloc_master(&pdev->dev, sizeof(*mcfqspi));
 	if (master == NULL) {
 		dev_dbg(&pdev->dev, "spi_alloc_master failed\n");
-- 
1.8.1.2



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Re: [PATCH] spi: coldfire-qspi: Prevent NULL pointer dereference

[Steven King]

On Saturday 08 March 2014 10:11:10 pm Axel Lin wrote:
> If pdata->cs_control is NULL, we will hit NULL pointer dereference in
> mcfqspi_cs_select() and mcfqspi_cs_deselect(). Thus add NULL test for
> pdata->cs_control in probe().
>

NAK.

 I suggest you read the code again.  There is no NULL pointer dereference and 
further, by returning an error if cs_control is NULL, you've now broken the 
design which was that cs_control is optional.
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Re: [PATCH] spi: coldfire-qspi: Prevent NULL pointer dereference

[Steven King]

On Saturday 08 March 2014 10:11:10 pm Axel Lin wrote:
> If pdata->cs_control is NULL, we will hit NULL pointer dereference in
> mcfqspi_cs_select() and mcfqspi_cs_deselect(). Thus add NULL test for
> pdata->cs_control in probe().


D'oh!  My bad.  Actually you're right there would be a NULL pointer 
dereference in cs_select and cs_deselect  (I was looking at the cs_setup and 
cs_teardown in the patch) and so cs_control must not be NULL.  Thats want I 
get for replying before I've had my coffee and when I haven't looked at the 
code in awhile.  So yeah, the patch is GTG.
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Re: [PATCH] spi: coldfire-qspi: Prevent NULL pointer dereference

[Mark Brown]

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On Mon, Mar 10, 2014 at 08:48:40AM -0700, Steven King wrote:
> On Saturday 08 March 2014 10:11:10 pm Axel Lin wrote:

> > If pdata->cs_control is NULL, we will hit NULL pointer dereference in
> > mcfqspi_cs_select() and mcfqspi_cs_deselect(). Thus add NULL test for
> > pdata->cs_control in probe().

> NAK.

>  I suggest you read the code again.  There is no NULL pointer dereference and 
> further, by returning an error if cs_control is NULL, you've now broken the 
> design which was that cs_control is optional.

So, you've sent this after I'd applied the patch (having ignored prior
patches as well, the last activity was in 2012), that's a bit
unfortunate.  I've reverted the patch but please if you're reviewing
changes to the driver can you indicate if things are OK when you do so -
if patches aren't getting any review from people working on the driver
the tendency is to assume that the driver has been abandoned.

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Re: [PATCH] spi: coldfire-qspi: Prevent NULL pointer dereference

[Geert Uytterhoeven]

On Mon, Mar 10, 2014 at 5:04 PM, Steven King <sfking-xS0NTnu2YfYAvxtiuMwx3w@public.gmane.org> wrote:
> On Saturday 08 March 2014 10:11:10 pm Axel Lin wrote:
>> If pdata->cs_control is NULL, we will hit NULL pointer dereference in
>> mcfqspi_cs_select() and mcfqspi_cs_deselect(). Thus add NULL test for
>> pdata->cs_control in probe().
>
> D'oh!  My bad.  Actually you're right there would be a NULL pointer
> dereference in cs_select and cs_deselect  (I was looking at the cs_setup and
> cs_teardown in the patch) and so cs_control must not be NULL.  Thats want I
> get for replying before I've had my coffee and when I haven't looked at the
> code in awhile.  So yeah, the patch is GTG.

I had the same first impression. But after looking through the code, the
changes is fine. Furthermore, there's only on in-tree user it, which does
provide cs_control.

There's more opportunity for cleanup, though, as cs_control provides control
of a GPIO, which can be handled by the SPI core, too.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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Re: [PATCH] spi: coldfire-qspi: Prevent NULL pointer dereference

[Mark Brown]

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On Mon, Mar 10, 2014 at 09:04:05AM -0700, Steven King wrote:

> D'oh!  My bad.  Actually you're right there would be a NULL pointer 
> dereference in cs_select and cs_deselect  (I was looking at the cs_setup and 
> cs_teardown in the patch) and so cs_control must not be NULL.  Thats want I 
> get for replying before I've had my coffee and when I haven't looked at the 
> code in awhile.  So yeah, the patch is GTG.

Hrm, I managed to make the same mistake when I redid the verification
somehow.  Odd.  Anyway, reinstated the patch.

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