RE: [PATCH v3] mfd: syscon: Decouple syscon interface from platform devices

[Pankaj Dubey <pankaj.dubey@samsung.com>]

Hi,

Adding CC to Xiubo Li, Geert Uytterhoeven and Stephen Warren. 

On Thursday, September 18, 2014, Dong Aisheng wrote,
> On Wed, Sep 17, 2014 at 04:50:50PM +0530, Pankaj Dubey wrote:
> > Hi,
> >
> > On Wednesday, September 17, 2014, Dong Aisheng Wrote,
> > > >
> > > > +	regmap = regmap_init_mmio(NULL, base,
&syscon_regmap_config);
> > >
> > > Does a NULL device pointer work?
> >
> > Yes, it is safe, at least we are able to test on Exynos based SoC.
> > I have tested it with kgene/for-next kernel on Exynos3250.
> > Also it has been tested on Exynos5250 based Snow board with 3.17-rc5
> > based kernel by Vivek Gautam.
> >
> > Patch V2 also has been tested by "Borris Brezillon" on AT91 platform.
> >
> >
> 
> The kernel i tested was next-20140915 of linux-next.
> 
> please see regmap_get_val_endian called in regmap_init function.
> static enum regmap_endian regmap_get_val_endian(struct device *dev,
>                                         const struct regmap_bus *bus,
>                                         const struct regmap_config
*config) {
>         struct device_node *np = dev->of_node;
>         enum regmap_endian endian;
> ...
> }
> It will crash at the first line of dev->of_node if dev is NULL.
> 
> Can you check if you're using the same code as mine?

No, it's not same.
My bad that I was not using linux-next for testing this patch.
We tested on kgene/for-next where these changes still have not come.
Just now I checked linux-next and found that it will crash at first line of 
"regmap_get_val_endian" as there is no check for NULL on dev.

I checked git history of regmap.c file and found recently this file has been
modified
for adding DT endianness binding support. Following are set of patches gone
for this

cf673fb regmap: Split regmap_get_endian() in two functions
5844a8b regmap: Fix handling of volatile registers for format_write() chips
45e1a27 regmap: of_regmap_get_endian() cleanup
ba1b53f regmap: Fix DT endianess parsing logic
d647c19 regmap: add DT endianness binding support.

I think there should have been a check for NULL on "dev" in
"regmap_get_val_endian", so that if dev pointer exist then only it makes
sense to get
endianness property from DT. 

I will suggest following fix in regmap.c for this. With following fix I
tested it and it works well
on linux-next also. So if you can confirm following fix is working for you
then I can post this
patch.

--------------------------------------------
Subject: [PATCH] regmap: fix NULL pointer dereference in
 regmap_get_val_endian

Recent commits for getting reg endianess causing NULL pointer
dereference if dev is passed NULL in regmap_init_mmio. This patch
fixes this issue, and allows to parse reg endianess only if dev
and dev->of_node exist.

Signed-off-by: Pankaj Dubey <pankaj.dubey@samsung.com>
---
 drivers/base/regmap/regmap.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index f2281af..455a877 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -477,7 +477,7 @@ static enum regmap_endian regmap_get_val_endian(struct
device *dev,
 					const struct regmap_bus *bus,
 					const struct regmap_config *config)
 {
-	struct device_node *np = dev->of_node;
+	struct device_node *np;
 	enum regmap_endian endian;
 
 	/* Retrieve the endianness specification from the regmap config */
@@ -487,15 +487,20 @@ static enum regmap_endian regmap_get_val_endian(struct
device *dev,
 	if (endian != REGMAP_ENDIAN_DEFAULT)
 		return endian;
 
-	/* Parse the device's DT node for an endianness specification */
-	if (of_property_read_bool(np, "big-endian"))
-		endian = REGMAP_ENDIAN_BIG;
-	else if (of_property_read_bool(np, "little-endian"))
-		endian = REGMAP_ENDIAN_LITTLE;
+	/* If the dev and dev->of_node exist try to get endianness from DT
*/
+	if (dev && dev->of_node) {
+		np = dev->of_node;
 
-	/* If the endianness was specified in DT, use that */
-	if (endian != REGMAP_ENDIAN_DEFAULT)
-		return endian;
+		/* Parse the device's DT node for an endianness
specification */
+		if (of_property_read_bool(np, "big-endian"))
+			endian = REGMAP_ENDIAN_BIG;
+		else if (of_property_read_bool(np, "little-endian"))
+			endian = REGMAP_ENDIAN_LITTLE;
+
+		/* If the endianness was specified in DT, use that */
+		if (endian != REGMAP_ENDIAN_DEFAULT)
+			return endian;
+	}
 
 	/* Retrieve the endianness specification from the bus config */
 	if (bus && bus->val_format_endian_default)
--

Thanks,
Pankaj Dubey

> Regards
> Dong Aisheng
> 
> >
> > Thanks,
> > Pankaj Dubey
> >
> > > Regards
> > > Dong Aisheng
> > >
> > > >
> > > >
> > > > _______________________________________________
> > > > linux-arm-kernel mailing list
> > > > linux-arm-kernel@lists.infradead.org
> > > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> >