[PATCH 1/2] of: fix of_device_get_modalias returned length when truncating buffers

[PATCH 1/2] of: fix of_device_get_modalias returned length when truncating buffers

[Rob Herring]

If the length of the modalias is greater than the buffer size, then the
modalias is truncated. However the untruncated length is returned which
will cause an error. Fix this to return the truncated length. If an error
in the case was desired, then then we should just return -ENOMEM.

The reality is no device will ever have 4KB of compatible strings to hit
this case.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
---
 drivers/of/device.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/of/device.c b/drivers/of/device.c
index fd5cfad7c403..bd620452f255 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -223,7 +223,7 @@ ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len)
 			str[i] = '_';
 	}
 
-	return tsize;
+	return repend;
 }
 
 /**
-- 
2.10.1

[PATCH 2/2] of: Add function for generating a DT modalias with a newline

[Rob Herring]

The modalias sysfs attr is lacking a newline for DT aliases on platform
devices. The macio and ibmebus correctly add the newline, but open code it.
Introduce a new function, of_device_modalias(), that fills the buffer with
the modalias including the newline and update users of the old
of_device_get_modalias function.

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/platforms/pseries/ibmebus.c |  5 +----
 drivers/base/platform.c                  |  2 +-
 drivers/macintosh/macio_sysfs.c          |  7 +------
 drivers/of/device.c                      | 16 +++++++++++++++-
 include/linux/of_device.h                |  7 +++----
 5 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/ibmebus.c b/arch/powerpc/platforms/pseries/ibmebus.c
index 614c28537141..18f5a7a2896f 100644
--- a/arch/powerpc/platforms/pseries/ibmebus.c
+++ b/arch/powerpc/platforms/pseries/ibmebus.c
@@ -410,10 +410,7 @@ static ssize_t name_show(struct device *dev,
 static ssize_t modalias_show(struct device *dev,
 				struct device_attribute *attr, char *buf)
 {
-	ssize_t len = of_device_get_modalias(dev, buf, PAGE_SIZE - 2);
-	buf[len] = '\n';
-	buf[len+1] = 0;
-	return len+1;
+	return of_device_modalias(dev, buf, PAGE_SIZE);
 }
 
 static struct device_attribute ibmebus_bus_device_attrs[] = {
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index c4af00385502..d92f60d7f15d 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -837,7 +837,7 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *a,
 	struct platform_device	*pdev = to_platform_device(dev);
 	int len;
 
-	len = of_device_get_modalias(dev, buf, PAGE_SIZE -1);
+	len = of_device_modalias(dev, buf, PAGE_SIZE);
 	if (len != -ENODEV)
 		return len;
 
diff --git a/drivers/macintosh/macio_sysfs.c b/drivers/macintosh/macio_sysfs.c
index 8eb40afbd0f5..0b1f9c76c68d 100644
--- a/drivers/macintosh/macio_sysfs.c
+++ b/drivers/macintosh/macio_sysfs.c
@@ -41,12 +41,7 @@ compatible_show (struct device *dev, struct device_attribute *attr, char *buf)
 static ssize_t modalias_show (struct device *dev, struct device_attribute *attr,
 			      char *buf)
 {
-	int len = of_device_get_modalias(dev, buf, PAGE_SIZE - 2);
-
-	buf[len] = '\n';
-	buf[len+1] = 0;
-
-	return len+1;
+	return of_device_modalias(dev, buf, PAGE_SIZE);
 }
 
 static ssize_t devspec_show(struct device *dev,
diff --git a/drivers/of/device.c b/drivers/of/device.c
index bd620452f255..f3c3108d5a3a 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -176,7 +176,7 @@ const void *of_device_get_match_data(const struct device *dev)
 }
 EXPORT_SYMBOL(of_device_get_match_data);
 
-ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len)
+static ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len)
 {
 	const char *compat;
 	int cplen, i;
@@ -227,6 +227,20 @@ ssize_t of_device_get_modalias(struct device *dev, char *str, ssize_t len)
 }
 
 /**
+ * of_device_modalias - Fill buffer with newline terminated modalias string
+ */
+ssize_t of_device_modalias(struct device *dev, char *str, ssize_t len)
+{
+	ssize_t sl = of_device_get_modalias(dev, str, len - 2);
+	if (sl < 0)
+		return sl;
+
+	str[sl++] = '\n';
+	str[sl] = 0;
+	return sl;
+}
+
+/**
  * of_device_uevent - Display OF related uevent information
  */
 void of_device_uevent(struct device *dev, struct kobj_uevent_env *env)
diff --git a/include/linux/of_device.h b/include/linux/of_device.h
index cc7dd687a89d..971d7250a8a4 100644
--- a/include/linux/of_device.h
+++ b/include/linux/of_device.h
@@ -35,8 +35,7 @@ extern void of_device_unregister(struct platform_device *ofdev);
 
 extern const void *of_device_get_match_data(const struct device *dev);
 
-extern ssize_t of_device_get_modalias(struct device *dev,
-					char *str, ssize_t len);
+extern ssize_t of_device_modalias(struct device *dev, char *str, ssize_t len);
 
 extern void of_device_uevent(struct device *dev, struct kobj_uevent_env *env);
 extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env);
@@ -72,8 +71,8 @@ static inline const void *of_device_get_match_data(const struct device *dev)
 	return NULL;
 }
 
-static inline int of_device_get_modalias(struct device *dev,
-				   char *str, ssize_t len)
+static inline int of_device_modalias(struct device *dev,
+				     char *str, ssize_t len)
 {
 	return -ENODEV;
 }
-- 
2.10.1

Re: [PATCH 2/2] of: Add function for generating a DT modalias with a newline

[Greg Kroah-Hartman]

On Mon, Jan 16, 2017 at 02:41:22PM -0600, Rob Herring wrote:
> The modalias sysfs attr is lacking a newline for DT aliases on platform
> devices. The macio and ibmebus correctly add the newline, but open code it.
> Introduce a new function, of_device_modalias(), that fills the buffer with
> the modalias including the newline and update users of the old
> of_device_get_modalias function.
> 
> Signed-off-by: Rob Herring <robh@kernel.org>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Frank Rowand <frowand.list@gmail.com>
> Cc: linuxppc-dev@lists.ozlabs.org


Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>