The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
1a3887924a7e ("efi: libstub: Disable struct randomization") cc49c71d2abe ("efi/libstub: Disable Shadow Call Stack")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 1a3887924a7e6edd331be76da7bf4c1e8eab4b1e Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel ardb@kernel.org Date: Mon, 22 Aug 2022 19:20:33 +0200 Subject: [PATCH] efi: libstub: Disable struct randomization
The EFI stub is a wrapper around the core kernel that makes it look like a EFI compatible PE/COFF application to the EFI firmware. EFI applications run on top of the EFI runtime, which is heavily based on so-called protocols, which are struct types consisting [mostly] of function pointer members that are instantiated and recorded in a protocol database.
These structs look like the ideal randomization candidates to the randstruct plugin (as they only carry function pointers), but of course, these protocols are contracts between the firmware that exposes them, and the EFI applications (including our stubbed kernel) that invoke them. This means that struct randomization for EFI protocols is not a great idea, and given that the stub shares very little data with the core kernel that is represented as a randomizable struct, we're better off just disabling it completely here.
Cc: stable@vger.kernel.org # v4.14+ Reported-by: Daniel Marth daniel.marth@inso.tuwien.ac.at Tested-by: Daniel Marth daniel.marth@inso.tuwien.ac.at Signed-off-by: Ard Biesheuvel ardb@kernel.org Acked-by: Kees Cook keescook@chromium.org
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index d0537573501e..2c67f71f2375 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -37,6 +37,13 @@ KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \ $(call cc-option,-fno-addrsig) \ -D__DISABLE_EXPORTS
+# +# struct randomization only makes sense for Linux internal types, which the EFI +# stub code never touches, so let's turn off struct randomization for the stub +# altogether +# +KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS)) + # remove SCS flags from all objects in this directory KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) # disable LTO