Re: [REGRESSION] x86/entry: Tracer no longer has opportunity to change the syscall number at entry via orig_ax

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

On Sun, Sep 13 2020 at 17:44, Michael Ellerman wrote:
> Kees Cook <keescook@xxxxxxxxxxxx> writes:
> diff --git a/kernel/entry/common.c b/kernel/entry/common.c
> index 18683598edbc..901361e2f8ea 100644
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
> @@ -60,13 +60,15 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
>                         return ret;
>         }
>  
> +       syscall = syscall_get_nr(current, regs);
> +
>         if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
>                 trace_sys_enter(regs, syscall);
>  
>         syscall_enter_audit(regs, syscall);
>  
>         /* The above might have changed the syscall number */
> -       return ret ? : syscall_get_nr(current, regs);
> +       return ret ? : syscall;
>  }

Yup, this looks right. Can you please send a proper patch?

Thanks,

        tglx