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

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Message-ID: <20090126185648.GD31918@localhost>
Date:	Mon, 26 Jan 2009 21:56:48 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.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

[Hiroshi Shimamoto - Mon, Jan 26, 2009 at 10:31:03AM -0800]
| 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.

Hiroshi, to be fair -- I just don't know what the
right solution would be ;-) I just noticed that
default: here a bit useless since we do 'testing'
the (from->si_code >> 16) after default: anyway.

So choose one /since I'm not really familiar with
process management in kernel/ :)

		-- Cyrill --
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