On Mon, Feb 10, 2025 at 09:28:25PM -0500, Nathan Chancellor wrote:
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.
Nice catch.
Cc: stable@vger.kernel.org Fixes: a2ff95e018f1 ("ACPI: platform: Add platform profile support") Reported-by: John Rowley lkml@johnrowley.me Closes: https://github.com/ClangBuiltLinux/linux/issues/2047 Tested-by: John Rowley lkml@johnrowley.me Reviewed-by: Sami Tolvanen samitolvanen@google.com Signed-off-by: Nathan Chancellor nathan@kernel.org
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-v...
I'll never find that, so be prepared for a "FAILED" email when this hits Linus's tree :)
Acked-by: Greg Kroah-Hartman gregkh@linuxfoundation.org