[PATCH v2 0/3] hwmon: Handle const struct attributes

[PATCH v2 0/3] hwmon: Handle const struct attributes

[Thomas Weißschuh]

Statically allocated instance of 'struct attribute' and its derivates
like 'struct device_attribute' are never modified.
To avoid accidental or malicious modifications (to hijack control flow)
they should be marked as 'const' and moved into read-only memory.
Historically the sysfs APIs did not allow this, but today it is possible.

Change the attributes in the hwmon core and also lay the groundwork for
the drivers to be changed.

The drivers themselves will also need to
be adapted. Please tell me in which form you want this to happen.
One big patch or per-driver patches; in a big series or separate?
Cc all driver maintainers or just hwmon core ones?

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Changes in v2:
- s/__DRIVER_ATTR/__DEVICE_ATTR/
- Link to v1: https://patch.msgid.link/20260805-sysfs-const-attr-hwmon-v1-0-4c0cb2b290a1@weissschuh.net

---
Thomas Weißschuh (3):
      hwmon: (core) Constify device attributes
      hwmon: (core) Use const APIs for the dynamically allocated sysfs attributes
      hwmon: (sysfs) Allow drivers to register const attributes

 drivers/hwmon/hwmon.c       | 70 ++++++++++++++++++++++-----------------------
 include/linux/hwmon-sysfs.h | 14 ++++-----
 2 files changed, 42 insertions(+), 42 deletions(-)
---
base-commit: ef9d75d6705d89d019d950262a11d55b19f5d9e3
change-id: 20260526-sysfs-const-attr-hwmon-f3b5692d2923

Best regards,
--  
Thomas Weißschuh <linux@weissschuh.net>

[PATCH v2 1/3] hwmon: (core) Constify device attributes

[Thomas Weißschuh]

Mark the attribute structures as const, as they are never modified.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/hwmon/hwmon.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
index 55a9a3ddd4aa..84108a16ef60 100644
--- a/drivers/hwmon/hwmon.c
+++ b/drivers/hwmon/hwmon.c
@@ -71,27 +71,27 @@ struct hwmon_thermal_data {
 };
 
 static ssize_t
-name_show(struct device *dev, struct device_attribute *attr, char *buf)
+name_show(struct device *dev, const struct device_attribute *attr, char *buf)
 {
 	return sysfs_emit(buf, "%s\n", to_hwmon_device(dev)->name);
 }
-static DEVICE_ATTR_RO(name);
+static const DEVICE_ATTR_RO(name);
 
 static ssize_t
-label_show(struct device *dev, struct device_attribute *attr, char *buf)
+label_show(struct device *dev, const struct device_attribute *attr, char *buf)
 {
 	return sysfs_emit(buf, "%s\n", to_hwmon_device(dev)->label);
 }
-static DEVICE_ATTR_RO(label);
+static const DEVICE_ATTR_RO(label);
 
-static struct attribute *hwmon_dev_attrs[] = {
+static const struct attribute *const hwmon_dev_attrs[] = {
 	&dev_attr_name.attr,
 	&dev_attr_label.attr,
 	NULL
 };
 
 static umode_t hwmon_dev_attr_is_visible(struct kobject *kobj,
-					 struct attribute *attr, int n)
+					 const struct attribute *attr, int n)
 {
 	struct device *dev = kobj_to_dev(kobj);
 	struct hwmon_device *hdev = to_hwmon_device(dev);
@@ -106,8 +106,8 @@ static umode_t hwmon_dev_attr_is_visible(struct kobject *kobj,
 }
 
 static const struct attribute_group hwmon_dev_attr_group = {
-	.attrs		= hwmon_dev_attrs,
-	.is_visible	= hwmon_dev_attr_is_visible,
+	.attrs_const		= hwmon_dev_attrs,
+	.is_visible_const	= hwmon_dev_attr_is_visible,
 };
 
 static const struct attribute_group *hwmon_dev_attr_groups[] = {

-- 
2.55.0

Re: [PATCH v2 1/3] hwmon: (core) Constify device attributes

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Incomplete constification of device attributes: the `pec` attribute was missed.
--

--- Patch [1]: [PATCH v2 1/3] hwmon: (core) Constify device attributes ---
commit 63bf6c9fac5c27892b6188fad21e12ff51c4b53a
Author: Thomas Weißschuh <linux@weissschuh.net>

hwmon: (core) Constify device attributes

This commit updates the hwmon core to mark device attribute structures as const
since they are never modified. It also updates the show callbacks and visibility
functions to accept const arguments.

> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
> index 55a9a3ddd4aac..84108a16ef60c 100644
> --- a/drivers/hwmon/hwmon.c
> +++ b/drivers/hwmon/hwmon.c
> @@ -71,27 +71,27 @@ struct hwmon_thermal_data {
>  };
>  
>  static ssize_t
> -name_show(struct device *dev, struct device_attribute *attr, char *buf)
> +name_show(struct device *dev, const struct device_attribute *attr, char *buf)
>  {
>  	return sysfs_emit(buf, "%s\n", to_hwmon_device(dev)->name);
>  }
> -static DEVICE_ATTR_RO(name);
> +static const DEVICE_ATTR_RO(name);
>  
>  static ssize_t
> -label_show(struct device *dev, struct device_attribute *attr, char *buf)
> +label_show(struct device *dev, const struct device_attribute *attr, char *buf)
>  {
>  	return sysfs_emit(buf, "%s\n", to_hwmon_device(dev)->label);
>  }
> -static DEVICE_ATTR_RO(label);
> +static const DEVICE_ATTR_RO(label);

[Severity: Low]
This isn't a bug, but should the pec attribute also be constified?

The pec attribute is defined further down in drivers/hwmon/hwmon.c but seems to
have been missed by this refactoring:

static ssize_t pec_show(struct device *dev, struct device_attribute *dummy,
			char *buf)

static ssize_t pec_store(struct device *dev, struct device_attribute *devattr,
			 const char *buf, size_t count)

static DEVICE_ATTR_RW(pec);

Since device_create_file() accepts a const struct device_attribute, could we
update pec_show(), pec_store(), and the pec device attribute to be const as
well?

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260806-sysfs-const-attr-hwmon-v2-0-22fee8b85509@weissschuh.net?part=1

Re: [PATCH v2 1/3] hwmon: (core) Constify device attributes

[Guenter Roeck]

On Thu, Aug 06, 2026 at 08:09:11AM +0200, Thomas Weißschuh wrote:
> Mark the attribute structures as const, as they are never modified.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Applied.

Thanks,
Guenter

[PATCH v2 2/3] hwmon: (core) Use const APIs for the dynamically allocated sysfs attributes

[Thomas Weißschuh]

The non-const sysfs attribute APIs are going to go away at some point.

Switch to the const variants to prepare for that.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/hwmon/hwmon.c | 54 +++++++++++++++++++++++++--------------------------
 1 file changed, 27 insertions(+), 27 deletions(-)

diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
index 84108a16ef60..90ceb815f43e 100644
--- a/drivers/hwmon/hwmon.c
+++ b/drivers/hwmon/hwmon.c
@@ -57,8 +57,8 @@ struct hwmon_device_attribute {
 };
 
 #define to_hwmon_attr(d) \
-	container_of(d, struct hwmon_device_attribute, dev_attr)
-#define to_dev_attr(a) container_of(a, struct device_attribute, attr)
+	container_of_const(d, struct hwmon_device_attribute, dev_attr)
+#define to_dev_attr(a) container_of_const(a, struct device_attribute, attr)
 
 /*
  * Thermal zone information
@@ -115,13 +115,13 @@ static const struct attribute_group *hwmon_dev_attr_groups[] = {
 	NULL
 };
 
-static void hwmon_free_attrs(struct attribute **attrs)
+static void hwmon_free_attrs(const struct attribute *const *attrs)
 {
 	int i;
 
 	for (i = 0; attrs[i]; i++) {
-		struct device_attribute *dattr = to_dev_attr(attrs[i]);
-		struct hwmon_device_attribute *hattr = to_hwmon_attr(dattr);
+		const struct device_attribute *dattr = to_dev_attr(attrs[i]);
+		const struct hwmon_device_attribute *hattr = to_hwmon_attr(dattr);
 
 		kfree(hattr);
 	}
@@ -132,8 +132,8 @@ static void hwmon_dev_release(struct device *dev)
 {
 	struct hwmon_device *hwdev = to_hwmon_device(dev);
 
-	if (hwdev->group.attrs)
-		hwmon_free_attrs(hwdev->group.attrs);
+	if (hwdev->group.attrs_const)
+		hwmon_free_attrs(hwdev->group.attrs_const);
 	kfree(hwdev->groups);
 	kfree(hwdev->label);
 	kfree(hwdev);
@@ -425,9 +425,9 @@ static int hwmon_pec_register(struct device *hdev)
 /* sysfs attribute management */
 
 static ssize_t hwmon_attr_show(struct device *dev,
-			       struct device_attribute *devattr, char *buf)
+			       const struct device_attribute *devattr, char *buf)
 {
-	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
+	const struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
 	struct hwmon_device *hwdev = to_hwmon_device(dev);
 	s64 val64;
 	long val;
@@ -450,10 +450,10 @@ static ssize_t hwmon_attr_show(struct device *dev,
 }
 
 static ssize_t hwmon_attr_show_string(struct device *dev,
-				      struct device_attribute *devattr,
+				      const struct device_attribute *devattr,
 				      char *buf)
 {
-	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
+	const struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
 	struct hwmon_device *hwdev = to_hwmon_device(dev);
 	enum hwmon_sensor_types type = hattr->type;
 	const char *s;
@@ -473,10 +473,10 @@ static ssize_t hwmon_attr_show_string(struct device *dev,
 }
 
 static ssize_t hwmon_attr_store(struct device *dev,
-				struct device_attribute *devattr,
+				const struct device_attribute *devattr,
 				const char *buf, size_t count)
 {
-	struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
+	const struct hwmon_device_attribute *hattr = to_hwmon_attr(devattr);
 	struct hwmon_device *hwdev = to_hwmon_device(dev);
 	long val;
 	int ret;
@@ -510,12 +510,12 @@ static bool is_string_attr(enum hwmon_sensor_types type, u32 attr)
 	       (type == hwmon_fan && attr == hwmon_fan_label);
 }
 
-static struct attribute *hwmon_genattr(const void *drvdata,
-				       enum hwmon_sensor_types type,
-				       u32 attr,
-				       int index,
-				       const char *template,
-				       const struct hwmon_ops *ops)
+static const struct attribute *hwmon_genattr(const void *drvdata,
+					     enum hwmon_sensor_types type,
+					     u32 attr,
+					     int index,
+					     const char *template,
+					     const struct hwmon_ops *ops)
 {
 	struct hwmon_device_attribute *hattr;
 	struct device_attribute *dattr;
@@ -552,8 +552,8 @@ static struct attribute *hwmon_genattr(const void *drvdata,
 	hattr->ops = ops;
 
 	dattr = &hattr->dev_attr;
-	dattr->show = is_string ? hwmon_attr_show_string : hwmon_attr_show;
-	dattr->store = hwmon_attr_store;
+	dattr->show_const = is_string ? hwmon_attr_show_string : hwmon_attr_show;
+	dattr->store_const = hwmon_attr_store;
 
 	a = &dattr->attr;
 	sysfs_attr_init(a);
@@ -831,7 +831,7 @@ static int hwmon_num_channel_attrs(const struct hwmon_channel_info *info)
 }
 
 static int hwmon_genattrs(const void *drvdata,
-			  struct attribute **attrs,
+			  const struct attribute **attrs,
 			  const struct hwmon_ops *ops,
 			  const struct hwmon_channel_info *info)
 {
@@ -850,7 +850,7 @@ static int hwmon_genattrs(const void *drvdata,
 		u32 attr;
 
 		while (attr_mask) {
-			struct attribute *a;
+			const struct attribute *a;
 
 			attr = __ffs(attr_mask);
 			attr_mask &= ~BIT(attr);
@@ -869,11 +869,11 @@ static int hwmon_genattrs(const void *drvdata,
 	return aindex;
 }
 
-static struct attribute **
+static const struct attribute **
 __hwmon_create_attrs(const void *drvdata, const struct hwmon_chip_info *chip)
 {
 	int ret, i, aindex = 0, nattrs = 0;
-	struct attribute **attrs;
+	const struct attribute **attrs;
 
 	for (i = 0; chip->info[i]; i++)
 		nattrs += hwmon_num_channel_attrs(chip->info[i]);
@@ -928,7 +928,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
 	hdev = &hwdev->dev;
 
 	if (chip) {
-		struct attribute **attrs;
+		const struct attribute **attrs;
 		int ngroups = 2; /* terminating NULL plus &hwdev->groups */
 
 		if (groups)
@@ -947,7 +947,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
 			goto free_hwmon;
 		}
 
-		hwdev->group.attrs = attrs;
+		hwdev->group.attrs_const = attrs;
 		ngroups = 0;
 		hwdev->groups[ngroups++] = &hwdev->group;
 

-- 
2.55.0

Re: [PATCH v2 2/3] hwmon: (core) Use const APIs for the dynamically allocated sysfs attributes

[sashiko-bot]

> The non-const sysfs attribute APIs are going to go away at some point.
> 
> Switch to the const variants to prepare for that.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260806-sysfs-const-attr-hwmon-v2-0-22fee8b85509@weissschuh.net?part=2

Re: [PATCH v2 2/3] hwmon: (core) Use const APIs for the dynamically allocated sysfs attributes

[Guenter Roeck]

On Thu, Aug 06, 2026 at 08:09:12AM +0200, Thomas Weißschuh wrote:
> The non-const sysfs attribute APIs are going to go away at some point.
> 
> Switch to the const variants to prepare for that.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Applied.

Thanks,
Guenter

[PATCH v2 3/3] hwmon: (sysfs) Allow drivers to register const attributes

[Thomas Weißschuh]

Switch to the __DEVICE_ATTR() macro which can handle callbacks taking
both const and non-const attribute structure arguments.
Allow the step-wise migration of the drivers.

Also use container_of_const() over container_of() to avoid casting away
the constness accidentally.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 include/linux/hwmon-sysfs.h | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/hwmon-sysfs.h b/include/linux/hwmon-sysfs.h
index d896713359cd..ee5b33185b2d 100644
--- a/include/linux/hwmon-sysfs.h
+++ b/include/linux/hwmon-sysfs.h
@@ -15,10 +15,10 @@ struct sensor_device_attribute{
 	int index;
 };
 #define to_sensor_dev_attr(_dev_attr) \
-	container_of(_dev_attr, struct sensor_device_attribute, dev_attr)
+	container_of_const(_dev_attr, struct sensor_device_attribute, dev_attr)
 
-#define SENSOR_ATTR(_name, _mode, _show, _store, _index)	\
-	{ .dev_attr = __ATTR(_name, _mode, _show, _store),	\
+#define SENSOR_ATTR(_name, _mode, _show, _store, _index)		\
+	{ .dev_attr = __DEVICE_ATTR(_name, _mode, _show, _store),	\
 	  .index = _index }
 
 #define SENSOR_ATTR_RO(_name, _func, _index)			\
@@ -49,11 +49,11 @@ struct sensor_device_attribute_2 {
 	u8 nr;
 };
 #define to_sensor_dev_attr_2(_dev_attr) \
-	container_of(_dev_attr, struct sensor_device_attribute_2, dev_attr)
+	container_of_const(_dev_attr, struct sensor_device_attribute_2, dev_attr)
 
-#define SENSOR_ATTR_2(_name, _mode, _show, _store, _nr, _index)	\
-	{ .dev_attr = __ATTR(_name, _mode, _show, _store),	\
-	  .index = _index,					\
+#define SENSOR_ATTR_2(_name, _mode, _show, _store, _nr, _index)		\
+	{ .dev_attr = __DEVICE_ATTR(_name, _mode, _show, _store),	\
+	  .index = _index,						\
 	  .nr = _nr }
 
 #define SENSOR_ATTR_2_RO(_name, _func, _nr, _index)		\

-- 
2.55.0

Re: [PATCH v2 3/3] hwmon: (sysfs) Allow drivers to register const attributes

[sashiko-bot]

> Switch to the __DEVICE_ATTR() macro which can handle callbacks taking
> both const and non-const attribute structure arguments.
> Allow the step-wise migration of the drivers.
> 
> Also use container_of_const() over container_of() to avoid casting away
> the constness accidentally.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260806-sysfs-const-attr-hwmon-v2-0-22fee8b85509@weissschuh.net?part=3

Re: [PATCH v2 3/3] hwmon: (sysfs) Allow drivers to register const attributes

[Guenter Roeck]

On Thu, Aug 06, 2026 at 08:09:13AM +0200, Thomas Weißschuh wrote:
> Switch to the __DEVICE_ATTR() macro which can handle callbacks taking
> both const and non-const attribute structure arguments.
> Allow the step-wise migration of the drivers.
> 
> Also use container_of_const() over container_of() to avoid casting away
> the constness accidentally.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Applied.

Thanks,
Guenter