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416de0246f
When booting a kernel with CONFIG_CFI_CLANG, there is a CFI failure when
accessing any of the values under
/sys/devices/system/cpu/intel_uncore_frequency/package_00_die_00:
$ cat /sys/devices/system/cpu/intel_uncore_frequency/package_00_die_00/max_freq_khz
fish: Job 1, 'cat /sys/devices/system/cpu/int…' terminated by signal SIGSEGV (Address boundary error)
$ sudo dmesg &| grep 'CFI failure'
[ 170.953925] CFI failure at kobj_attr_show+0x19/0x30 (target: show_max_freq_khz+0x0/0xc0 [intel_uncore_frequency_common]; expected type: 0xd34078c5
The sysfs callback functions such as show_domain_id() are written as if
they are going to be called by dev_attr_show() but as the above message
shows, they are instead called by kobj_attr_show(). kCFI checks that the
destination of an indirect jump has the exact same type as the prototype
of the function pointer it is called through and fails when they do not.
These callbacks are called through kobj_attr_show() because
uncore_root_kobj was initialized with kobject_create_and_add(), which
means uncore_root_kobj has a ->sysfs_ops of kobj_sysfs_ops from
kobject_create(), which uses kobj_attr_show() as its ->show() value.
The only reason there has not been a more noticeable problem until this
point is that 'struct kobj_attribute' and 'struct device_attribute' have
the same layout, so getting the callback from container_of() works the
same with either value.
Change all the callbacks and their uses to be compatible with
kobj_attr_show() and kobj_attr_store(), which resolves the kCFI failure
and allows the sysfs files to work properly.
Closes: https://github.com/ClangBuiltLinux/linux/issues/1974
Fixes:
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|---|---|---|
| .. | ||
| chrome | ||
| goldfish | ||
| loongarch | ||
| mellanox | ||
| mips | ||
| olpc | ||
| surface | ||
| x86 | ||
| Kconfig | ||
| Makefile | ||