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

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Message-Id: <20240819-acpi-platform_profile-fix-cfi-violation-v1-1-479365d848f6@kernel.org>
Date: Mon, 19 Aug 2024 12:09:22 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>
Cc: Hans de Goede <hdegoede@...hat.com>, 
 Mark Pearson <markpearson@...ovo.com>, Kees Cook <kees@...nel.org>, 
 Sami Tolvanen <samitolvanen@...gle.com>, linux-acpi@...r.kernel.org, 
 linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, patches@...ts.linux.dev, 
 stable@...r.kernel.org, John Rowley <lkml@...nrowley.me>, 
 Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] ACPI: platform-profile: Fix CFI violation when accessing
 sysfs files

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)

This happens to work because the layout of 'struct kobj_attribute' and
'struct device_attribute' are the same, so the container_of() cast
happens to allow the callbacks to still work.

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@...r.kernel.org
Fixes: a2ff95e018f1 ("ACPI: platform: Add platform profile support")
Reported-by: John Rowley <lkml@...nrowley.me>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2047
Tested-by: John Rowley <lkml@...nrowley.me>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/acpi/platform_profile.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
index d2f7fd7743a1..11278f785526 100644
--- a/drivers/acpi/platform_profile.c
+++ b/drivers/acpi/platform_profile.c
@@ -22,8 +22,8 @@ static const char * const profile_names[] = {
 };
 static_assert(ARRAY_SIZE(profile_names) == PLATFORM_PROFILE_LAST);
 
-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)
 {
 	int len = 0;
@@ -49,8 +49,8 @@ static ssize_t platform_profile_choices_show(struct device *dev,
 	return len;
 }
 
-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_BALANCED;
@@ -77,8 +77,8 @@ static ssize_t platform_profile_show(struct device *dev,
 	return sysfs_emit(buf, "%s\n", profile_names[profile]);
 }
 
-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)
 {
 	int err, i;
@@ -115,12 +115,12 @@ 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: 47ac09b91befbb6a235ab620c32af719f8208399
change-id: 20240819-acpi-platform_profile-fix-cfi-violation-de278753bd5f

Best regards,
-- 
Nathan Chancellor <nathan@...nel.org>