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Message-ID: <CAAhV-H5ezCcC=2zvumhbsEu0U8Y4YWbLmG9soYKQB=fr0PohbA@mail.gmail.com>
Date: Wed, 23 Apr 2025 22:02:41 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Youling Tang <youling.tang@...ux.dev>
Cc: Ard Biesheuvel <ardb@...nel.org>, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
Youling Tang <tangyouling@...inos.cn>
Subject: Re: [PATCH] LoongArch: Enable HAVE_ARCH_STACKLEAK
Hi, Youling,
On Wed, Apr 23, 2025 at 2:32 PM Youling Tang <youling.tang@...ux.dev> wrote:
>
> From: Youling Tang <tangyouling@...inos.cn>
>
> Add support for the stackleak feature. It initialize the stack with the
> poison value before returning from system calls which improves the kernel
> security.
>
> At the same time, disables the plugin in EFI stub code because EFI stub
> is out of scope for the protection.
>
> Tested on 3A5000 (enable CONFIG_GCC_PLUGIN_STACKLEAK and CONFIG_LKDTM):
> # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT
> # dmesg
> lkdtm: Performing direct entry STACKLEAK_ERASING
> lkdtm: stackleak stack usage:
> high offset: 320 bytes
> current: 448 bytes
> lowest: 1264 bytes
> tracked: 1264 bytes
> untracked: 208 bytes
> poisoned: 14528 bytes
> low offset: 64 bytes
> lkdtm: OK: the rest of the thread stack is properly erased
>
> Signed-off-by: Youling Tang <tangyouling@...inos.cn>
> ---
> arch/loongarch/Kconfig | 1 +
> arch/loongarch/include/asm/entry-common.h | 8 +-------
> arch/loongarch/include/asm/stacktrace.h | 5 +++++
> arch/loongarch/kernel/entry.S | 9 +++++++++
> drivers/firmware/efi/libstub/Makefile | 2 +-
> 5 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 067c0b994648..3a6bfcab2dde 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -122,6 +122,7 @@ config LOONGARCH
> select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
> select HAVE_ARCH_SECCOMP
> select HAVE_ARCH_SECCOMP_FILTER
> + select HAVE_ARCH_STACKLEAK
> select HAVE_ARCH_TRACEHOOK
> select HAVE_ARCH_TRANSPARENT_HUGEPAGE
> select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
> diff --git a/arch/loongarch/include/asm/entry-common.h b/arch/loongarch/include/asm/entry-common.h
> index 0fe2a098ded9..a7a6af490f86 100644
> --- a/arch/loongarch/include/asm/entry-common.h
> +++ b/arch/loongarch/include/asm/entry-common.h
> @@ -2,12 +2,6 @@
> #ifndef ARCH_LOONGARCH_ENTRY_COMMON_H
> #define ARCH_LOONGARCH_ENTRY_COMMON_H
>
> -#include <linux/sched.h>
> -#include <linux/processor.h>
> -
> -static inline bool on_thread_stack(void)
> -{
> - return !(((unsigned long)(current->stack) ^ current_stack_pointer) & ~(THREAD_SIZE - 1));
> -}
> +#include <asm/stacktrace.h>
>
> #endif
> diff --git a/arch/loongarch/include/asm/stacktrace.h b/arch/loongarch/include/asm/stacktrace.h
> index fc8b64773794..3861beb96002 100644
> --- a/arch/loongarch/include/asm/stacktrace.h
> +++ b/arch/loongarch/include/asm/stacktrace.h
> @@ -31,6 +31,11 @@ bool in_irq_stack(unsigned long stack, struct stack_info *info);
> bool in_task_stack(unsigned long stack, struct task_struct *task, struct stack_info *info);
> int get_stack_info(unsigned long stack, struct task_struct *task, struct stack_info *info);
>
> +static inline bool on_thread_stack(void)
Use __always_inline is better for objtool, like x86.
> +{
> + return !(((unsigned long)(current->stack) ^ current_stack_pointer) & ~(THREAD_SIZE - 1));
> +}
> +
> #define STR_LONG_L __stringify(LONG_L)
> #define STR_LONG_S __stringify(LONG_S)
> #define STR_LONGSIZE __stringify(LONGSIZE)
> diff --git a/arch/loongarch/kernel/entry.S b/arch/loongarch/kernel/entry.S
> index 48e7e34e355e..27dcb3a66b2b 100644
> --- a/arch/loongarch/kernel/entry.S
> +++ b/arch/loongarch/kernel/entry.S
> @@ -16,6 +16,12 @@
> #include <asm/thread_info.h>
> #include <asm/unwind_hints.h>
>
> + .macro STACKLEAK_ERASE
> +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> + bl stackleak_erase_on_task_stack
> +#endif
> + .endm
Move this macro to stackframe.h? This makes it can be used by other files.
Huacai
> +
> .text
> .cfi_sections .debug_frame
> .align 5
> @@ -73,6 +79,7 @@ SYM_CODE_START(handle_syscall)
> move a0, sp
> bl do_syscall
>
> + STACKLEAK_ERASE
> RESTORE_ALL_AND_RET
> SYM_CODE_END(handle_syscall)
> _ASM_NOKPROBE(handle_syscall)
> @@ -82,6 +89,7 @@ SYM_CODE_START(ret_from_fork)
> bl schedule_tail # a0 = struct task_struct *prev
> move a0, sp
> bl syscall_exit_to_user_mode
> + STACKLEAK_ERASE
> RESTORE_STATIC
> RESTORE_SOME
> RESTORE_SP_AND_RET
> @@ -94,6 +102,7 @@ SYM_CODE_START(ret_from_kernel_thread)
> jirl ra, s0, 0
> move a0, sp
> bl syscall_exit_to_user_mode
> + STACKLEAK_ERASE
> RESTORE_STATIC
> RESTORE_SOME
> RESTORE_SP_AND_RET
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index d23a1b9fed75..b97981d63d2f 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -31,7 +31,7 @@ cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \
> $(DISABLE_STACKLEAK_PLUGIN)
> cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax \
> $(DISABLE_STACKLEAK_PLUGIN)
> -cflags-$(CONFIG_LOONGARCH) += -fpie
> +cflags-$(CONFIG_LOONGARCH) += -fpie $(DISABLE_STACKLEAK_PLUGIN)
>
> cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
>
> --
> 2.38.1
>
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