[PATCH] riscv: Randomize lower bits of stack address

[Alexandre Ghiti]

Hi Yunhui,

On Thu, Aug 15, 2024 at 4:08 AM yunhui cui <cuiyunhui at bytedance.com> wrote:
>
> A gentle ping, Any more comments on this patch?

I'm adding @Kees Cook  in cc in case he has any.

Thanks,

Alex

>
> On Thu, Jul 11, 2024 at 2:09 PM yunhui cui <cuiyunhui at bytedance.com> wrote:
> >
> > 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
>
> Thanks,
> Yunhui