On Fri, Feb 16, 2024 at 05:38:55PM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > The ACPI custom_method debugfs interface is security-sensitive and > concurrent access to it is broken [1]. > > Moreover, the recipe for preparing a customized version of a given > control method has changed at one point due to ACPICA changes, which > has not been reflected in its documentation, so whoever used it before > has had to adapt and it had gone unnoticed for a long time. > > This interface was a bad idea to start with and its implementation is > fragile at the design level. It's been always conceptually questionable, > problematic from the security standpoint and implemented poorly. > > Patches fixing its most apparent functional issues (for example, [2]) don't > actually address much of the above. > > Granted, at the time it was introduced, there was no alternative, but > there is the AML debugger in the kernel now and there is the configfs > interface allowing custom ACPI tables to be loaded. The former can be > used for extensive AML debugging and the latter can be use for testing > new AML. [3] > > Accordingly, drop custom_method along with its (outdated anyway) > documentation. > > Link: https://lore.kernel.org/linux-acpi/20221227063335.61474-1-zh.nvgt@xxxxxxxxx/ # [1] > https://lore.kernel.org/linux-acpi/20231111132402.4142-1-shiqiang.deng213@xxxxxxxxx/ [2] > https://stackoverflow.com/questions/62849113/how-to-unload-an-overlay-loaded-using-acpi-config-sysfs # [3] > Reported-by: Hang Zhang <zh.nvgt@xxxxxxxxx> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Yay! Happy to see this removed. :) Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -- Kees Cook
