loadpin: Prevent SECURITY_LOADPIN_ENFORCE=y without module decompression

If modules are built compressed, and LoadPin is enforcing by default, we
must have in-kernel module decompression enabled (MODULE_DECOMPRESS).
Modules will fail to load without decompression built into the kernel
because they'll be blocked by LoadPin. Add a depends on clause to
prevent this combination.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20240514224839.2526112-1-swboyd@chromium.orgSigned-off-by: Kees Cook <keescook@chromium.org>

security/loadpin/Kconfig

@@ -14,6 +14,9 @@ config SECURITY_LOADPIN
 config SECURITY_LOADPIN_ENFORCE
 	bool "Enforce LoadPin at boot"
 	depends on SECURITY_LOADPIN
+	# Module compression breaks LoadPin unless modules are decompressed in
+	# the kernel.
+	depends on !MODULES || (MODULE_COMPRESS_NONE || MODULE_DECOMPRESS)
 	help
 	  If selected, LoadPin will enforce pinning at boot. If not
 	  selected, it can be enabled at boot with the kernel parameter