| Message ID | 20240704-shadow-call-stack-v3-2-d11c7a6ebe30@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Rust and the shadow call stack sanitizer | expand |
Hi Alice, On Thu, Jul 04, 2024 at 03:07:58PM +0000, Alice Ryhl wrote: > As of rustc 1.80.0, the Rust compiler supports the -Zfixed-x18 flag, so > we can now use Rust with the shadow call stack sanitizer. > > On older versions of Rust, it is possible to use shadow call stack by > passing -Ctarget-feature=+reserve-x18 instead of -Zfixed-x18. However, > this flag emits a warning, so this patch does not add support for that. > > Currently, the compiler thinks that the aarch64-unknown-none target > doesn't support -Zsanitizer=shadow-call-stack, so the build will fail if > you enable shadow call stack in non-dynamic mode. See [2] for the ^ this should be [1]? > feature request to add this. Kconfig is not configured to reject this > configuration because that leads to cyclic Kconfig rules. While it probably does not matter much given Rust for Linux is still "in the works", I think it would be good to avoid these build failures. Perhaps something like this could work (which basically just forces on UNWIND_PATCH_PAC_INTO_SCS when Rust is enabled). diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 5d91259ee7b5..a9f08a2bd1c6 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -89,7 +89,7 @@ config ARM64 select ARCH_SUPPORTS_DEBUG_PAGEALLOC select ARCH_SUPPORTS_HUGETLBFS select ARCH_SUPPORTS_MEMORY_FAILURE - select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK + select ARCH_SUPPORTS_SHADOW_CALL_STACK if CC_HAVE_SHADOW_CALL_STACK && (!RUST || CAN_UNWIND_PATCH_PAC_INTO_SCS) select ARCH_SUPPORTS_LTO_CLANG if CPU_LITTLE_ENDIAN select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_SUPPORTS_CFI_CLANG @@ -2262,12 +2262,16 @@ config STACKPROTECTOR_PER_TASK def_bool y depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_SYSREG -config UNWIND_PATCH_PAC_INTO_SCS - bool "Enable shadow call stack dynamically using code patching" +config CAN_UNWIND_PATCH_PAC_INTO_SCS + def_bool y # needs Clang with https://github.com/llvm/llvm-project/commit/de07cde67b5d205d58690be012106022aea6d2b3 incorporated depends on CC_IS_CLANG && CLANG_VERSION >= 150000 depends on ARM64_PTR_AUTH_KERNEL && CC_HAS_BRANCH_PROT_PAC_RET - depends on SHADOW_CALL_STACK + +config UNWIND_PATCH_PAC_INTO_SCS + bool "Enable shadow call stack dynamically using code patching" if !RUST + depends on SHADOW_CALL_STACK && CAN_UNWIND_PATCH_PAC_INTO_SCS + default y if RUST select UNWIND_TABLES select DYNAMIC_SCS Otherwise, it might be good to wait to enable this until [1] is addressed, but I don't really feel that strongly about it. From a Kconfig/Kbuild perspective, the rest of the patch seems fine. > Link: https://github.com/rust-lang/rust/issues/121972 [1] > Signed-off-by: Alice Ryhl <aliceryhl@google.com> > --- > Makefile | 1 + > arch/Kconfig | 2 +- > arch/arm64/Makefile | 3 +++ > 3 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index c11a10c8e710..4ae741601a1c 100644 > --- a/Makefile > +++ b/Makefile > @@ -945,6 +945,7 @@ ifdef CONFIG_SHADOW_CALL_STACK > ifndef CONFIG_DYNAMIC_SCS > CC_FLAGS_SCS := -fsanitize=shadow-call-stack > KBUILD_CFLAGS += $(CC_FLAGS_SCS) > +KBUILD_RUSTFLAGS += -Zsanitizer=shadow-call-stack > endif > export CC_FLAGS_SCS > endif > diff --git a/arch/Kconfig b/arch/Kconfig > index 238448a9cb71..5a6e296df5e6 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -690,7 +690,7 @@ config SHADOW_CALL_STACK > bool "Shadow Call Stack" > depends on ARCH_SUPPORTS_SHADOW_CALL_STACK > depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER > - depends on !RUST > + depends on !RUST || RUSTC_VERSION >= 108000 > depends on MMU > help > This option enables the compiler's Shadow Call Stack, which > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 3f0f35fd5bb7..bbf313ddd700 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -57,9 +57,11 @@ KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) > ifneq ($(CONFIG_UNWIND_TABLES),y) > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables > KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables > +KBUILD_RUSTFLAGS += -Cforce-unwind-tables=n > else > KBUILD_CFLAGS += -fasynchronous-unwind-tables > KBUILD_AFLAGS += -fasynchronous-unwind-tables > +KBUILD_RUSTFLAGS += -Cforce-unwind-tables=y -Zuse-sync-unwind=n > endif > > ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) > @@ -114,6 +116,7 @@ endif > > ifeq ($(CONFIG_SHADOW_CALL_STACK), y) > KBUILD_CFLAGS += -ffixed-x18 > +KBUILD_RUSTFLAGS += -Zfixed-x18 > endif > > ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) > > -- > 2.45.2.803.g4e1b14247a-goog >
On Thu, Jul 04, 2024 at 03:07:58PM +0000, Alice Ryhl wrote: > As of rustc 1.80.0, the Rust compiler supports the -Zfixed-x18 flag, so > we can now use Rust with the shadow call stack sanitizer. > > On older versions of Rust, it is possible to use shadow call stack by > passing -Ctarget-feature=+reserve-x18 instead of -Zfixed-x18. However, > this flag emits a warning, so this patch does not add support for that. > > Currently, the compiler thinks that the aarch64-unknown-none target > doesn't support -Zsanitizer=shadow-call-stack, so the build will fail if > you enable shadow call stack in non-dynamic mode. See [2] for the > feature request to add this. Kconfig is not configured to reject this > configuration because that leads to cyclic Kconfig rules. > > Link: https://github.com/rust-lang/rust/issues/121972 [1] > Signed-off-by: Alice Ryhl <aliceryhl@google.com> > --- > Makefile | 1 + > arch/Kconfig | 2 +- > arch/arm64/Makefile | 3 +++ > 3 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/Makefile b/Makefile > index c11a10c8e710..4ae741601a1c 100644 > --- a/Makefile > +++ b/Makefile > @@ -945,6 +945,7 @@ ifdef CONFIG_SHADOW_CALL_STACK > ifndef CONFIG_DYNAMIC_SCS > CC_FLAGS_SCS := -fsanitize=shadow-call-stack > KBUILD_CFLAGS += $(CC_FLAGS_SCS) > +KBUILD_RUSTFLAGS += -Zsanitizer=shadow-call-stack > endif > export CC_FLAGS_SCS > endif > diff --git a/arch/Kconfig b/arch/Kconfig > index 238448a9cb71..5a6e296df5e6 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -690,7 +690,7 @@ config SHADOW_CALL_STACK > bool "Shadow Call Stack" > depends on ARCH_SUPPORTS_SHADOW_CALL_STACK > depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER > - depends on !RUST > + depends on !RUST || RUSTC_VERSION >= 108000 > depends on MMU > help > This option enables the compiler's Shadow Call Stack, which For these security related options, like CFI_CLANG or RANDSTRUCT, I'm inclined to say that RUST is actually what should grow the depends on. That way it'll be RUST that gets silently disabled in configs when patch 1 gets backported (where it is mostly useless anyway) rather than SCS nor will it disable SCS when someone enables RUST in their config, instead it'd be a conscious choice. Cheers, Conor.
On Thu, Jul 4, 2024 at 10:17 AM Conor Dooley <conor@kernel.org> wrote: > > For these security related options, like CFI_CLANG or RANDSTRUCT, I'm > inclined to say that RUST is actually what should grow the depends on. > That way it'll be RUST that gets silently disabled in configs when patch > 1 gets backported (where it is mostly useless anyway) rather than SCS > nor will it disable SCS when someone enables RUST in their config, > instead it'd be a conscious choice. I agree, we shouldn't silently disable hardening features when Rust is enabled. Sami
On Thu, Jul 4, 2024 at 7:17 PM Conor Dooley <conor@kernel.org> wrote: > > On Thu, Jul 04, 2024 at 03:07:58PM +0000, Alice Ryhl wrote: > > As of rustc 1.80.0, the Rust compiler supports the -Zfixed-x18 flag, so > > we can now use Rust with the shadow call stack sanitizer. > > > > On older versions of Rust, it is possible to use shadow call stack by > > passing -Ctarget-feature=+reserve-x18 instead of -Zfixed-x18. However, > > this flag emits a warning, so this patch does not add support for that. > > > > Currently, the compiler thinks that the aarch64-unknown-none target > > doesn't support -Zsanitizer=shadow-call-stack, so the build will fail if > > you enable shadow call stack in non-dynamic mode. See [2] for the > > feature request to add this. Kconfig is not configured to reject this > > configuration because that leads to cyclic Kconfig rules. > > > > Link: https://github.com/rust-lang/rust/issues/121972 [1] > > Signed-off-by: Alice Ryhl <aliceryhl@google.com> > > --- > > Makefile | 1 + > > arch/Kconfig | 2 +- > > arch/arm64/Makefile | 3 +++ > > 3 files changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/Makefile b/Makefile > > index c11a10c8e710..4ae741601a1c 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -945,6 +945,7 @@ ifdef CONFIG_SHADOW_CALL_STACK > > ifndef CONFIG_DYNAMIC_SCS > > CC_FLAGS_SCS := -fsanitize=shadow-call-stack > > KBUILD_CFLAGS += $(CC_FLAGS_SCS) > > +KBUILD_RUSTFLAGS += -Zsanitizer=shadow-call-stack > > endif > > export CC_FLAGS_SCS > > endif > > diff --git a/arch/Kconfig b/arch/Kconfig > > index 238448a9cb71..5a6e296df5e6 100644 > > --- a/arch/Kconfig > > +++ b/arch/Kconfig > > @@ -690,7 +690,7 @@ config SHADOW_CALL_STACK > > bool "Shadow Call Stack" > > depends on ARCH_SUPPORTS_SHADOW_CALL_STACK > > depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER > > - depends on !RUST > > + depends on !RUST || RUSTC_VERSION >= 108000 > > depends on MMU > > help > > This option enables the compiler's Shadow Call Stack, which > > For these security related options, like CFI_CLANG or RANDSTRUCT, I'm > inclined to say that RUST is actually what should grow the depends on. > That way it'll be RUST that gets silently disabled in configs when patch > 1 gets backported (where it is mostly useless anyway) rather than SCS > nor will it disable SCS when someone enables RUST in their config, > instead it'd be a conscious choice. Okay, I'll make that change. I suspect this will also break the Kconfig cycle mentioned in the commit message. Thanks for the suggestion! Alice
On Tue, Jul 9, 2024 at 2:10 AM Sami Tolvanen <samitolvanen@google.com> wrote: > > On Thu, Jul 4, 2024 at 10:17 AM Conor Dooley <conor@kernel.org> wrote: > > > > For these security related options, like CFI_CLANG or RANDSTRUCT, I'm > > inclined to say that RUST is actually what should grow the depends on. > > That way it'll be RUST that gets silently disabled in configs when patch > > 1 gets backported (where it is mostly useless anyway) rather than SCS > > nor will it disable SCS when someone enables RUST in their config, > > instead it'd be a conscious choice. > > I agree, we shouldn't silently disable hardening features when Rust is enabled. That definitely wasn't my intention. I'll update it for v4. Alice
diff --git a/Makefile b/Makefile index c11a10c8e710..4ae741601a1c 100644 --- a/Makefile +++ b/Makefile @@ -945,6 +945,7 @@ ifdef CONFIG_SHADOW_CALL_STACK ifndef CONFIG_DYNAMIC_SCS CC_FLAGS_SCS := -fsanitize=shadow-call-stack KBUILD_CFLAGS += $(CC_FLAGS_SCS) +KBUILD_RUSTFLAGS += -Zsanitizer=shadow-call-stack endif export CC_FLAGS_SCS endif diff --git a/arch/Kconfig b/arch/Kconfig index 238448a9cb71..5a6e296df5e6 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -690,7 +690,7 @@ config SHADOW_CALL_STACK bool "Shadow Call Stack" depends on ARCH_SUPPORTS_SHADOW_CALL_STACK depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER - depends on !RUST + depends on !RUST || RUSTC_VERSION >= 108000 depends on MMU help This option enables the compiler's Shadow Call Stack, which diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 3f0f35fd5bb7..bbf313ddd700 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -57,9 +57,11 @@ KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) ifneq ($(CONFIG_UNWIND_TABLES),y) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables +KBUILD_RUSTFLAGS += -Cforce-unwind-tables=n else KBUILD_CFLAGS += -fasynchronous-unwind-tables KBUILD_AFLAGS += -fasynchronous-unwind-tables +KBUILD_RUSTFLAGS += -Cforce-unwind-tables=y -Zuse-sync-unwind=n endif ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) @@ -114,6 +116,7 @@ endif ifeq ($(CONFIG_SHADOW_CALL_STACK), y) KBUILD_CFLAGS += -ffixed-x18 +KBUILD_RUSTFLAGS += -Zfixed-x18 endif ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
As of rustc 1.80.0, the Rust compiler supports the -Zfixed-x18 flag, so we can now use Rust with the shadow call stack sanitizer. On older versions of Rust, it is possible to use shadow call stack by passing -Ctarget-feature=+reserve-x18 instead of -Zfixed-x18. However, this flag emits a warning, so this patch does not add support for that. Currently, the compiler thinks that the aarch64-unknown-none target doesn't support -Zsanitizer=shadow-call-stack, so the build will fail if you enable shadow call stack in non-dynamic mode. See [2] for the feature request to add this. Kconfig is not configured to reject this configuration because that leads to cyclic Kconfig rules. Link: https://github.com/rust-lang/rust/issues/121972 [1] Signed-off-by: Alice Ryhl <aliceryhl@google.com> --- Makefile | 1 + arch/Kconfig | 2 +- arch/arm64/Makefile | 3 +++ 3 files changed, 5 insertions(+), 1 deletion(-)