[PATCH] riscv: Randomize lower bits of stack address

[yunhui cui]

Add punit in the loop.


On Tue, Jun 25, 2024 at 11:05 AM Yunhui Cui <cuiyunhui at bytedance.com> wrote:
>
> Implement arch_align_stack() to randomize the lower bits
> of the stack address.
>
> Signed-off-by: Yunhui Cui <cuiyunhui at bytedance.com>
> ---
>  arch/riscv/include/asm/exec.h | 8 ++++++++
>  arch/riscv/kernel/process.c   | 9 +++++++++
>  2 files changed, 17 insertions(+)
>  create mode 100644 arch/riscv/include/asm/exec.h
>
> diff --git a/arch/riscv/include/asm/exec.h b/arch/riscv/include/asm/exec.h
> new file mode 100644
> index 000000000000..07d9942682e0
> --- /dev/null
> +++ b/arch/riscv/include/asm/exec.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef __ASM_EXEC_H
> +#define __ASM_EXEC_H
> +
> +extern unsigned long arch_align_stack(unsigned long sp);
> +
> +#endif /* __ASM_EXEC_H */
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index e4bc61c4e58a..e3142d8a6e28 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -15,6 +15,7 @@
>  #include <linux/tick.h>
>  #include <linux/ptrace.h>
>  #include <linux/uaccess.h>
> +#include <linux/personality.h>
>
>  #include <asm/unistd.h>
>  #include <asm/processor.h>
> @@ -26,6 +27,7 @@
>  #include <asm/cpuidle.h>
>  #include <asm/vector.h>
>  #include <asm/cpufeature.h>
> +#include <asm/exec.h>
>
>  #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
>  #include <linux/stackprotector.h>
> @@ -99,6 +101,13 @@ void show_regs(struct pt_regs *regs)
>                 dump_backtrace(regs, NULL, KERN_DEFAULT);
>  }
>
> +unsigned long arch_align_stack(unsigned long sp)
> +{
> +       if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
> +               sp -= get_random_u32_below(PAGE_SIZE);
> +       return sp & ~0xf;
> +}
> +
>  #ifdef CONFIG_COMPAT
>  static bool compat_mode_supported __read_mostly;
>
> --
> 2.20.1
>

Thanks,
Yunhui