[PATCH] powerpc/ptrace: Use copy_{from, to}_user() rather than open-coding

[Samuel Mendoza-Jonas]

On Tue, 2018-05-29 at 22:57 +1000, Michael Ellerman wrote:
> From: Al Viro <viro at ZenIV.linux.org.uk>
> 
> In PPC_PTRACE_GETHWDBGINFO and PPC_PTRACE_SETHWDEBUG we do an
> access_ok() check and then __copy_{from,to}_user().
> 
> Instead we should just use copy_{from,to}_user() which does all that
> for us and is less error prone.
> 
> Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Reviewed-by: Samuel Mendoza-Jonas <sam at mendozajonas.com>

> ---
>  arch/powerpc/kernel/ptrace.c | 20 ++++++--------------
>  1 file changed, 6 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
> index 0f63dd5972e9..9667666eb18e 100644
> --- a/arch/powerpc/kernel/ptrace.c
> +++ b/arch/powerpc/kernel/ptrace.c
> @@ -3082,27 +3082,19 @@ long arch_ptrace(struct task_struct *child, long request,
>  #endif /* CONFIG_HAVE_HW_BREAKPOINT */
>  #endif /* CONFIG_PPC_ADV_DEBUG_REGS */
>  
> -		if (!access_ok(VERIFY_WRITE, datavp,
> -			       sizeof(struct ppc_debug_info)))
> +		if (copy_to_user(datavp, &dbginfo,
> +				 sizeof(struct ppc_debug_info)))
>  			return -EFAULT;
> -		ret = __copy_to_user(datavp, &dbginfo,
> -				     sizeof(struct ppc_debug_info)) ?
> -		      -EFAULT : 0;
> -		break;
> +		return 0;
>  	}
>  
>  	case PPC_PTRACE_SETHWDEBUG: {
>  		struct ppc_hw_breakpoint bp_info;
>  
> -		if (!access_ok(VERIFY_READ, datavp,
> -			       sizeof(struct ppc_hw_breakpoint)))
> +		if (copy_from_user(&bp_info, datavp,
> +				   sizeof(struct ppc_hw_breakpoint)))
>  			return -EFAULT;
> -		ret = __copy_from_user(&bp_info, datavp,
> -				       sizeof(struct ppc_hw_breakpoint)) ?
> -		      -EFAULT : 0;
> -		if (!ret)
> -			ret = ppc_set_hwdebug(child, &bp_info);
> -		break;
> +		return ppc_set_hwdebug(child, &bp_info);
>  	}
>  
>  	case PPC_PTRACE_DELHWDEBUG: {