[PATCH v3] ACPI: platform-profile: Fix CFI violation when accessing sysfs files

[Nathan Chancellor]

When an attribute group is created with sysfs_create_group(), the
->sysfs_ops() callback is set to kobj_sysfs_ops, which sets the ->show()
and ->store() callbacks to kobj_attr_show() and kobj_attr_store()
respectively. These functions use container_of() to get the respective
callback from the passed attribute, meaning that these callbacks need to
be the same type as the callbacks in 'struct kobj_attribute'.

However, the platform_profile sysfs functions have the type of the
->show() and ->store() callbacks in 'struct device_attribute', which
results a CFI violation when accessing platform_profile or
platform_profile_choices under /sys/firmware/acpi because the types do
not match:

  CFI failure at kobj_attr_show+0x19/0x30 (target: platform_profile_choices_show+0x0/0x140; expected type: 0x7a69590c)

There is no functional issue from the type mismatch because the layout
of 'struct kobj_attribute' and 'struct device_attribute' are the same,
so the container_of() cast does not break anything aside from CFI.

Change the type of platform_profile_choices_show() and
platform_profile_{show,store}() to match the callbacks in
'struct kobj_attribute' and update the attribute variables to match,
which resolves the CFI violation.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: a2ff95e018f1 ("ACPI: platform: Add platform profile support")
Reported-by: John Rowley <lkml@xxxxxxxxxxxxx>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2047
Tested-by: John Rowley <lkml@xxxxxxxxxxxxx>
Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
Changes in v3:
- Rebase on 6.14-rc1, which includes updates to the driver to address
  Greg's previous concerns but this change is still needed for the
  legacy sysfs interface. v2 can be used for the stable backport.
- Link to v2: https://lore.kernel.org/r/20241118-acpi-platform_profile-fix-cfi-violation-v2-1-62ff952804de@xxxxxxxxxx

Changes in v2:
- Rebase on linux-pm/acpi
- Pick up Sami's reviewed-by tag
- Adjust wording around why there is no functional issue from the
  mismatched types
- Link to v1: https://lore.kernel.org/r/20240819-acpi-platform_profile-fix-cfi-violation-v1-1-479365d848f6@xxxxxxxxxx
---
 drivers/acpi/platform_profile.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
index fc92e43d0fe9..1b6317f759f9 100644
--- a/drivers/acpi/platform_profile.c
+++ b/drivers/acpi/platform_profile.c
@@ -260,14 +260,14 @@ static int _aggregate_choices(struct device *dev, void *data)
 
 /**
  * platform_profile_choices_show - Show the available profile choices for legacy sysfs interface
- * @dev: The device
+ * @kobj: The kobject
  * @attr: The attribute
  * @buf: The buffer to write to
  *
  * Return: The number of bytes written
  */
-static ssize_t platform_profile_choices_show(struct device *dev,
-					     struct device_attribute *attr,
+static ssize_t platform_profile_choices_show(struct kobject *kobj,
+					     struct kobj_attribute *attr,
 					     char *buf)
 {
 	unsigned long aggregate[BITS_TO_LONGS(PLATFORM_PROFILE_LAST)];
@@ -333,14 +333,14 @@ static int _store_and_notify(struct device *dev, void *data)
 
 /**
  * platform_profile_show - Show the current profile for legacy sysfs interface
- * @dev: The device
+ * @kobj: The kobject
  * @attr: The attribute
  * @buf: The buffer to write to
  *
  * Return: The number of bytes written
  */
-static ssize_t platform_profile_show(struct device *dev,
-				     struct device_attribute *attr,
+static ssize_t platform_profile_show(struct kobject *kobj,
+				     struct kobj_attribute *attr,
 				     char *buf)
 {
 	enum platform_profile_option profile = PLATFORM_PROFILE_LAST;
@@ -362,15 +362,15 @@ static ssize_t platform_profile_show(struct device *dev,
 
 /**
  * platform_profile_store - Set the profile for legacy sysfs interface
- * @dev: The device
+ * @kobj: The kobject
  * @attr: The attribute
  * @buf: The buffer to read from
  * @count: The number of bytes to read
  *
  * Return: The number of bytes read
  */
-static ssize_t platform_profile_store(struct device *dev,
-				      struct device_attribute *attr,
+static ssize_t platform_profile_store(struct kobject *kobj,
+				      struct kobj_attribute *attr,
 				      const char *buf, size_t count)
 {
 	unsigned long choices[BITS_TO_LONGS(PLATFORM_PROFILE_LAST)];
@@ -401,12 +401,12 @@ static ssize_t platform_profile_store(struct device *dev,
 	return count;
 }
 
-static DEVICE_ATTR_RO(platform_profile_choices);
-static DEVICE_ATTR_RW(platform_profile);
+static struct kobj_attribute attr_platform_profile_choices = __ATTR_RO(platform_profile_choices);
+static struct kobj_attribute attr_platform_profile = __ATTR_RW(platform_profile);
 
 static struct attribute *platform_profile_attrs[] = {
-	&dev_attr_platform_profile_choices.attr,
-	&dev_attr_platform_profile.attr,
+	&attr_platform_profile_choices.attr,
+	&attr_platform_profile.attr,
 	NULL
 };
 

---
base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
change-id: 20240819-acpi-platform_profile-fix-cfi-violation-de278753bd5f

Best regards,
-- 
Nathan Chancellor <nathan@xxxxxxxxxx>