[PATCH 5.11 256/601] ACPI: CPPC: Replace cppc_attr with kobj_attribute

Greg Kroah-Hartman
2021-05-12T17:31:07Z

From: Nathan Chancellor <nathan@kernel.org>

[ Upstream commit 2bc6262c6117dd18106d5aa50d53e945b5d99c51 ]

All of the CPPC sysfs show functions are called via indirect call in
kobj_attr_show(), where they should be of type

ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *attr, char *buf);

because that is the type of the ->show() member in
'struct kobj_attribute' but they are actually of type

ssize_t (*show)(struct kobject *kobj, struct attribute *attr, char *buf);

because of the ->show() member in 'struct cppc_attr', resulting in a
Control Flow Integrity violation [1].

$ cat /sys/devices/system/cpu/cpu0/acpi_cppc/highest_perf
3400

$ dmesg | grep "CFI failure"
[ 175.970559] CFI failure (target: show_highest_perf+0x0/0x8):

As far as I can tell, the only difference between 'struct cppc_attr'
and 'struct kobj_attribute' aside from the type of the attr parameter
is the type of the count parameter in the ->store() member (ssize_t vs.
size_t), which does not actually matter because all of these nodes are
read-only.

Eliminate 'struct cppc_attr' in favor of 'struct kobj_attribute' to fix
the violation.

[1]: https://lore.kernel.org/r/20210401233216.2540591-1-samitolvanen@google.com/

Fixes: 158c998ea44b ("ACPI / CPPC: add sysfs support to compute delivered performance")
Link: https://github.com/ClangBuiltLinux/linux/issues/1343
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/acpi/cppc_acpi.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 75aaf94ae0a9..f98b533d9aef 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -119,23 +119,15 @@ static DEFINE_PER_CPU(struct cpc_desc *, cpc_desc_ptr);
*/
#define NUM_RETRIES 500ULL

-struct cppc_attr {
- struct attribute attr;
- ssize_t (*show)(struct kobject *kobj,
- struct attribute *attr, char *buf);
- ssize_t (*store)(struct kobject *kobj,
- struct attribute *attr, const char *c, ssize_t count);
-};
-
#define define_one_cppc_ro(_name) \
-static struct cppc_attr _name = \
+static struct kobj_attribute _name = \
__ATTR(_name, 0444, show_##_name, NULL)

#define to_cpc_desc(a) container_of(a, struct cpc_desc, kobj)

#define show_cppc_data(access_fn, struct_name, member_name) \
static ssize_t show_##member_name(struct kobject *kobj, \
- struct attribute *attr, char *buf) \
+ struct kobj_attribute *attr, char *buf) \
{ \
struct cpc_desc *cpc_ptr = to_cpc_desc(kobj); \
struct struct_name st_name = {0}; \
@@ -161,7 +153,7 @@ show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, reference_perf);
show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time);

static ssize_t show_feedback_ctrs(struct kobject *kobj,
- struct attribute *attr, char *buf)
+ struct kobj_attribute *attr, char *buf)
{
struct cpc_desc *cpc_ptr = to_cpc_desc(kobj);
struct cppc_perf_fb_ctrs fb_ctrs = {0};
--
2.30.2