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    Subject[PATCH 5.10 225/530] ACPI: CPPC: Replace cppc_attr with kobj_attribute
    Date
    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 7a99b19bb893..0a2da06e9d8b 100644
    --- a/drivers/acpi/cppc_acpi.c
    +++ b/drivers/acpi/cppc_acpi.c
    @@ -118,23 +118,15 @@ 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}; \
    @@ -160,7 +152,7 @@ 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


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