Re: [PATCH RFC bpf-next 1/3] uprobe: Add uretprobe syscall to speed up return probe

[Oleg Nesterov <oleg@redhat.com>]

On 03/18, Jiri Olsa wrote:
>
> +SYSCALL_DEFINE0(uretprobe)
> +{
> +	struct pt_regs *regs = task_pt_regs(current);
> +	unsigned long sregs[3], err;
> +
> +	/*
> +	 * We set rax and syscall itself changes rcx and r11, so the syscall
> +	 * trampoline saves their original values on stack. We need to read
> +	 * them and set original register values and fix the rsp pointer back.
> +	 */
> +	err = copy_from_user((void *) &sregs, (void *) regs->sp, sizeof(sregs));
                                              ^^^^^^^^^^^^^^^^^

IIUC, it should be (void __user *)regs->sp to shut up the sparse checks.
The 1st "(void *)" typecast is not needed.

Correctness-wise looks good to me, FWIW

Reviewed-by: Oleg Nesterov <oleg@redhat.com>