linux-kernel - Re: [RFC v2 -tip 3/3] x86: ia32_signal: use {get|put}_user

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Message-ID: <497E0167.10604@ct.jp.nec.com>
Date:	Mon, 26 Jan 2009 10:31:03 -0800
From:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 -tip 3/3] x86: ia32_signal: use {get|put}_user_try and
 catch

Cyrill Gorcunov wrote:
> [Hiroshi Shimamoto - Fri, Jan 23, 2009 at 03:50:38PM -0800]
> | From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
> | 
> | Impact: use new framework
> | 
> | Use {get|put}_user_try, catch, and _ex in arch/x86/ia32/ia32_signal.c.
> | 
> | Note: this patch contains "WARNING: line over 80 characters", because when
> | introducing new block I insert an indent to avoid mistakes by edit.
> | 
> | Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
> | ---
> |  arch/x86/ia32/ia32_signal.c |  365 +++++++++++++++++++++++--------------------
> |  1 files changed, 195 insertions(+), 170 deletions(-)
> | 
> | diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
> | index 9dabd00..dd77ac0 100644
> | --- a/arch/x86/ia32/ia32_signal.c
> | +++ b/arch/x86/ia32/ia32_signal.c
> | @@ -46,78 +46,83 @@ void signal_fault(struct pt_regs *regs, void __user *frame, char *where);
> |
> ... 
> | +	put_user_try {
> | +		/* If you change siginfo_t structure, please make sure that
> | +		   this code is fixed accordingly.
> | +		   It should never copy any pad contained in the structure
> | +		   to avoid security leaks, but must copy the generic
> | +		   3 ints plus the relevant union member.  */
> | +		put_user_ex(from->si_signo, &to->si_signo);
> | +		put_user_ex(from->si_errno, &to->si_errno);
> | +		put_user_ex((short)from->si_code, &to->si_code);
> | +
> | +		if (from->si_code < 0) {
> | +			put_user_ex(from->si_pid, &to->si_pid);
> | +			put_user_ex(from->si_uid, &to->si_uid);
> | +			put_user_ex(ptr_to_compat(from->si_ptr), &to->si_ptr);
> | +		} else {
> | +			/*
> | +			 * First 32bits of unions are always present:
> | +			 * si_pid === si_band === si_tid === si_addr(LS half)
> | +			 */
> | +			put_user_ex(from->_sifields._pad[0],
> | +					  &to->_sifields._pad[0]);
> | +			switch (from->si_code >> 16) {
> | +			case __SI_FAULT >> 16:
> | +				break;
> | +			case __SI_CHLD >> 16:
> | +				put_user_ex(from->si_utime, &to->si_utime);
> | +				put_user_ex(from->si_stime, &to->si_stime);
> | +				put_user_ex(from->si_status, &to->si_status);
> | +				/* FALL THROUGH */
> | +			default:
> 
> Hi Hiroshi,

Hi Cyrill,

> 
> may I ask why we use default here?

I don't know:) Hm, it looks old code.
arch/i386/kernel/signal.c in 2.4 has similar code.

I guess this code didn't change when copy_siginfo_to_user() was moved
from arch/i386/kernel/signal.c to kernel/signal.c.

Should we change this like copy_siginfo_tu_user() in kernel/signal.c?
Copying si_pid was added in kernel/signal.c.

BTW, it seems same __ST_KILL and default.

Thanks,
Hiroshi

> 
> | +			case __SI_KILL >> 16:
> | +				put_user_ex(from->si_uid, &to->si_uid);
> | +				break;
> | +			case __SI_POLL >> 16:
> | +				put_user_ex(from->si_fd, &to->si_fd);
> | +				break;
> | +			case __SI_TIMER >> 16:
> | +				put_user_ex(from->si_overrun, &to->si_overrun);
> | +				put_user_ex(ptr_to_compat(from->si_ptr),
> | +					    &to->si_ptr);
> | +				break;
> | +				 /* This is not generated by the kernel as of now.  */
> | +			case __SI_RT >> 16:
> | +			case __SI_MESGQ >> 16:
> | +				put_user_ex(from->si_uid, &to->si_uid);
> | +				put_user_ex(from->si_int, &to->si_int);
> | +				break;
> | +			}
> |  		}
> | -	}
> | +	} put_user_catch(err);
> | +
> |  	return err;
> |  }
> |  
> ...
>  
> 		- Cyrill -
> --
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