Messages in this thread Patch in this message | | | Date | Wed, 15 Jan 2020 10:28:16 -0800 | Subject | [RFC PATCH] UML: add support for KASAN under x86_64 | From | Patricia Alfonso <> |
| |
Make KASAN run on User Mode Linux on x86_64.
The location of the KASAN shadow memory, starting at KASAN_SHADOW_OFFSET, can be configured using the KASAN_SHADOW_OFFSET option. UML uses roughly 18TB of address space, and KASAN requires 1/8th of this. For this reason, the default location is 0x100000000000. There is usually enough free space at this location; however, it is a config option so that it can be easily changed if needed.
Functions that are used before KASAN is initialized are excluded from instrumentation. The UML-specific KASAN initializer uses mmap to map the roughly 2.25TB of shadow memory to the location defined by KASAN_SHADOW_OFFSET and ensures that the address space used by the kernel text and the vmalloc region is not poisoned at initialization.
Signed-off-by: Patricia Alfonso <trishalfonso@google.com> --- arch/um/Kconfig | 10 ++++++++++ arch/um/include/asm/dma.h | 1 + arch/um/include/asm/kasan.h | 32 ++++++++++++++++++++++++++++++++ arch/um/kernel/Makefile | 4 ++++ arch/um/kernel/kasan_init_um.c | 20 ++++++++++++++++++++ arch/um/kernel/skas/Makefile | 6 ++++++ arch/um/kernel/um_arch.c | 3 +++ arch/um/os-Linux/mem.c | 18 ++++++++++++++++++ arch/um/os-Linux/user_syms.c | 4 ++-- arch/x86/um/Makefile | 3 ++- arch/x86/um/vdso/Makefile | 3 +++ kernel/Makefile | 6 ++++++ lib/Makefile | 10 ++++++++++ 13 files changed, 117 insertions(+), 3 deletions(-) create mode 100644 arch/um/include/asm/kasan.h create mode 100644 arch/um/kernel/kasan_init_um.c
diff --git a/arch/um/Kconfig b/arch/um/Kconfig index 6f0edd0c0220..99c68863e7e9 100644 --- a/arch/um/Kconfig +++ b/arch/um/Kconfig @@ -8,6 +8,7 @@ config UML select ARCH_HAS_KCOV select ARCH_NO_PREEMPT select HAVE_ARCH_AUDITSYSCALL + select HAVE_ARCH_KASAN select HAVE_ARCH_SECCOMP_FILTER select HAVE_ASM_MODVERSIONS select HAVE_UID16 @@ -198,6 +199,15 @@ config UML_TIME_TRAVEL_SUPPORT It is safe to say Y, but you probably don't need this. +config KASAN_SHADOW_OFFSET + hex + depends on KASAN + default 0x100000000000 + help + This is the offset at which the ~2.25TB of shadow memory is + initialized and used by KASAN for memory debugging. The default + is 0x100000000000. + endmenu source "arch/um/drivers/Kconfig" diff --git a/arch/um/include/asm/dma.h b/arch/um/include/asm/dma.h index fdc53642c718..8aafd60d62bb 100644 --- a/arch/um/include/asm/dma.h +++ b/arch/um/include/asm/dma.h @@ -5,6 +5,7 @@ #include <asm/io.h> extern unsigned long uml_physmem; +extern unsigned long long physmem_size; #define MAX_DMA_ADDRESS (uml_physmem) diff --git a/arch/um/include/asm/kasan.h b/arch/um/include/asm/kasan.h new file mode 100644 index 000000000000..ca4c43a35d41 --- /dev/null +++ b/arch/um/include/asm/kasan.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_UM_KASAN_H +#define __ASM_UM_KASAN_H + +#include <linux/init.h> +#include <linux/const.h> + +#define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) +#ifdef CONFIG_X86_64 +#define KASAN_SHADOW_SIZE 0x100000000000UL +#else +#error "KASAN_SHADOW_SIZE is not defined in this sub-architecture" +#endif + +// used in kasan_mem_to_shadow to divide by 8 +#define KASAN_SHADOW_SCALE_SHIFT 3 + +#define KASAN_SHADOW_START (KASAN_SHADOW_OFFSET) +#define KASAN_SHADOW_END (KASAN_SHADOW_START + KASAN_SHADOW_SIZE) + +#ifdef CONFIG_KASAN +void kasan_init(void); +void kasan_map_shadow(void); +#else +static inline void kasan_early_init(void) { } +static inline void kasan_init(void) { } +#endif /* CONFIG_KASAN */ + +void kasan_map_memory(void *start, unsigned long len); +void kasan_unpoison_shadow(const void *address, size_t size); + +#endif /* __ASM_UM_KASAN_H */ diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile index 5aa882011e04..f783a7dd863c 100644 --- a/arch/um/kernel/Makefile +++ b/arch/um/kernel/Makefile @@ -8,6 +8,9 @@ # kernel. KCOV_INSTRUMENT := n +# Do not instrument on main.o +KASAN_SANITIZE := n + CPPFLAGS_vmlinux.lds := -DSTART=$(LDS_START) \ -DELF_ARCH=$(LDS_ELF_ARCH) \ -DELF_FORMAT=$(LDS_ELF_FORMAT) \ @@ -24,6 +27,7 @@ obj-$(CONFIG_GPROF) += gprof_syms.o obj-$(CONFIG_GCOV) += gmon_syms.o obj-$(CONFIG_EARLY_PRINTK) += early_printk.o obj-$(CONFIG_STACKTRACE) += stacktrace.o +obj-$(CONFIG_KASAN) += kasan_init_um.o USER_OBJS := config.o diff --git a/arch/um/kernel/kasan_init_um.c b/arch/um/kernel/kasan_init_um.c new file mode 100644 index 000000000000..2e9a85216fb5 --- /dev/null +++ b/arch/um/kernel/kasan_init_um.c @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <asm/kasan.h> +#include <linux/sched.h> +#include <linux/sched/task.h> +#include <asm/dma.h> +#include <as-layout.h> + +void kasan_init(void) +{ + kasan_map_memory((void *)KASAN_SHADOW_START, KASAN_SHADOW_SIZE); + + // unpoison the kernel text which is form uml_physmem -> uml_reserved + kasan_unpoison_shadow((void *)uml_physmem, physmem_size); + + // unpoison the vmalloc region, which is start_vm -> end_vm + kasan_unpoison_shadow((void *)start_vm, (end_vm - start_vm + 1)); + + init_task.kasan_depth = 0; + pr_info("KernelAddressSanitizer initialized\n"); +} diff --git a/arch/um/kernel/skas/Makefile b/arch/um/kernel/skas/Makefile index f3d494a4fd9b..d68f447274e5 100644 --- a/arch/um/kernel/skas/Makefile +++ b/arch/um/kernel/skas/Makefile @@ -5,6 +5,12 @@ obj-y := clone.o mmu.o process.o syscall.o uaccess.o +ifdef CONFIG_UML +# Do not instrument until after start_uml() because KASAN is not +# initialized yet +KASAN_SANITIZE := n +endif + # clone.o is in the stub, so it can't be built with profiling # GCC hardened also auto-enables -fpic, but we need %ebx so it can't work -> # disable it diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c index 0f40eccbd759..73cd159d28e8 100644 --- a/arch/um/kernel/um_arch.c +++ b/arch/um/kernel/um_arch.c @@ -14,6 +14,7 @@ #include <linux/sched/task.h> #include <linux/kmsg_dump.h> +#include <asm/kasan.h> #include <asm/pgtable.h> #include <asm/processor.h> #include <asm/sections.h> @@ -227,6 +228,8 @@ static struct notifier_block panic_exit_notifier = { void uml_finishsetup(void) { + kasan_init(); + atomic_notifier_chain_register(&panic_notifier_list, &panic_exit_notifier); diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c index 3c1b77474d2d..ef282bacc58e 100644 --- a/arch/um/os-Linux/mem.c +++ b/arch/um/os-Linux/mem.c @@ -17,6 +17,24 @@ #include <init.h> #include <os.h> +/** + * kasan_map_memory() - maps memory from @start with a size of @len + * @start: the start address of the memory to be mapped + * @len: the length of the memory to be mapped + * + * This function is used to map shadow memory for KASAN in uml + */ +void kasan_map_memory(void *start, size_t len) +{ + if (mmap(start, + len, + PROT_READ|PROT_WRITE, + MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, + -1, + 0) == MAP_FAILED) + os_info("Couldn't allocate shadow memory %s", strerror(errno)); +} + /* Set by make_tempfile() during early boot. */ static char *tempdir = NULL; diff --git a/arch/um/os-Linux/user_syms.c b/arch/um/os-Linux/user_syms.c index 715594fe5719..cb667c9225ab 100644 --- a/arch/um/os-Linux/user_syms.c +++ b/arch/um/os-Linux/user_syms.c @@ -27,10 +27,10 @@ EXPORT_SYMBOL(strstr); #ifndef __x86_64__ extern void *memcpy(void *, const void *, size_t); EXPORT_SYMBOL(memcpy); -#endif - EXPORT_SYMBOL(memmove); EXPORT_SYMBOL(memset); +#endif + EXPORT_SYMBOL(printf); /* Here, instead, I can provide a fake prototype. Yes, someone cares: genksyms. diff --git a/arch/x86/um/Makefile b/arch/x86/um/Makefile index 33c51c064c77..7dbd76c546fe 100644 --- a/arch/x86/um/Makefile +++ b/arch/x86/um/Makefile @@ -26,7 +26,8 @@ else obj-y += syscalls_64.o vdso/ -subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o ../entry/thunk_64.o +subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o ../entry/thunk_64.o \ + ../lib/memmove_64.o ../lib/memset_64.o endif diff --git a/arch/x86/um/vdso/Makefile b/arch/x86/um/vdso/Makefile index 0caddd6acb22..450efa0fb694 100644 --- a/arch/x86/um/vdso/Makefile +++ b/arch/x86/um/vdso/Makefile @@ -3,6 +3,9 @@ # Building vDSO images for x86. # +# do not instrument on vdso because KASAN is not compatible with user mode +KASAN_SANITIZE := n + # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. KCOV_INSTRUMENT := n diff --git a/kernel/Makefile b/kernel/Makefile index f2cc0d118a0b..4fbb72cb253f 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -32,6 +32,12 @@ KCOV_INSTRUMENT_kcov.o := n KASAN_SANITIZE_kcov.o := n CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) +ifdef CONFIG_UML +# Do not istrument kasan on panic because it can be called before KASAN +# is initialized +KASAN_SANITIZE_panic.o := n +endif + # cond_syscall is currently not LTO compatible CFLAGS_sys_ni.o = $(DISABLE_LTO) diff --git a/lib/Makefile b/lib/Makefile index 93217d44237f..e28dc5b06ae2 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -17,6 +17,16 @@ KCOV_INSTRUMENT_list_debug.o := n KCOV_INSTRUMENT_debugobjects.o := n KCOV_INSTRUMENT_dynamic_debug.o := n +# Don't sanatize vsprintf or string functions in UM because they are used +# before KASAN is initialized from cmdline parsing cmdline and kstrtox are +# also called during uml initialization before KASAN is instrumented +ifdef CONFIG_UML +KASAN_SANITIZE_vsprintf.o := n +KASAN_SANITIZE_string.o := n +KASAN_SANITIZE_cmdline.o := n +KASAN_SANITIZE_kstrtox.o := n +endif + # Early boot use of cmdline, don't instrument it ifdef CONFIG_AMD_MEM_ENCRYPT KASAN_SANITIZE_string.o := n -- 2.25.0.rc1.283.g88dfdc4193-goog
| |