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KVM: arm64: Introduce CONFIG_UBSAN_KVM_EL2

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Add a new Kconfig CONFIG_UBSAN_KVM_EL2 for KVM which enables
UBSAN for EL2 code (in protected/nvhe/hvhe) modes.
This will re-use the same checks enabled for the kernel for
the hypervisor. The only difference is that for EL2 it always
emits a "brk" instead of implementing hooks as the hypervisor
can't print reports.

The KVM code will re-use the same code for the kernel
"report_ubsan_failure()" so #ifdefs are changed to also have this
code for CONFIG_UBSAN_KVM_EL2

Signed-off-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20250430162713.1997569-4-smostafa@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Mostafa Saleh 2025-04-30 16:27:10 +00:00 • committed by Marc Zyngier
parent d683a85618
commit 61b38f7591
5 changed files with 24 additions and 4 deletions
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6
arch/arm64/kvm/hyp/nvhe/Makefile
View file

@ -99,3 +99,9 @@ KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_FTRACE) $(CC_FLAGS_SCS), $(KBUILD_CFLAG
# causes a build failure. Remove profile optimization flags.
KBUILD_CFLAGS := $(filter-out -fprofile-sample-use=% -fprofile-use=%, $(KBUILD_CFLAGS))
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
ifeq ($(CONFIG_UBSAN_KVM_EL2),y)
UBSAN_SANITIZE := y
# Always use brk and not hooks
ccflags-y += $(CFLAGS_UBSAN_TRAP)
endif

2
include/linux/ubsan.h
View file

@ -2,7 +2,7 @@
#ifndef _LINUX_UBSAN_H
#define _LINUX_UBSAN_H
#ifdef CONFIG_UBSAN_TRAP
#if defined(CONFIG_UBSAN_TRAP) || defined(CONFIG_UBSAN_KVM_EL2)
const char *report_ubsan_failure(u32 check_type);
#else
static inline const char *report_ubsan_failure(u32 check_type)

9
lib/Kconfig.ubsan
View file

@ -165,4 +165,13 @@ config TEST_UBSAN
This is a test module for UBSAN.
It triggers various undefined behavior, and detect it.
config UBSAN_KVM_EL2
bool "UBSAN for KVM code at EL2"
depends on ARM64
help
Enable UBSAN when running on ARM64 with KVM in a split mode
(nvhe/hvhe/protected) for the hypervisor code running in EL2.
In this mode, any UBSAN violation in EL2 would panic the kernel
and information similar to UBSAN_TRAP would be printed.
endif # if UBSAN

6
lib/ubsan.c
View file

@ -19,7 +19,7 @@
#include "ubsan.h"
#ifdef CONFIG_UBSAN_TRAP
#if defined(CONFIG_UBSAN_TRAP) || defined(CONFIG_UBSAN_KVM_EL2)
/*
* Only include matches for UBSAN checks that are actually compiled in.
* The mappings of struct SanitizerKind (the -fsanitize=xxx args) to
@ -97,7 +97,9 @@ const char *report_ubsan_failure(u32 check_type)
}
}
#else
#endif
#ifndef CONFIG_UBSAN_TRAP
static const char * const type_check_kinds[] = {
"load of",
"store to",

5
scripts/Makefile.ubsan
View file

@ -1,5 +1,8 @@
# SPDX-License-Identifier: GPL-2.0
# Shared with KVM/arm64.
export CFLAGS_UBSAN_TRAP := $(call cc-option,-fsanitize-trap=undefined,-fsanitize-undefined-trap-on-error)
# Enable available and selected UBSAN features.
ubsan-cflags-$(CONFIG_UBSAN_ALIGNMENT) += -fsanitize=alignment
ubsan-cflags-$(CONFIG_UBSAN_BOUNDS_STRICT) += -fsanitize=bounds-strict
@ -10,7 +13,7 @@ ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO) += -fsanitize=integer-divide-by-zero
ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE) += -fsanitize=unreachable
ubsan-cflags-$(CONFIG_UBSAN_BOOL) += -fsanitize=bool
ubsan-cflags-$(CONFIG_UBSAN_ENUM) += -fsanitize=enum
ubsan-cflags-$(CONFIG_UBSAN_TRAP) += $(call cc-option,-fsanitize-trap=undefined,-fsanitize-undefined-trap-on-error)
ubsan-cflags-$(CONFIG_UBSAN_TRAP) += $(CFLAGS_UBSAN_TRAP)
export CFLAGS_UBSAN := $(ubsan-cflags-y)