linux-kernel - [patch] i386: remove unnecessary code

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Message-ID: <20070717160425.GA26401@elte.hu>
Date:	Tue, 17 Jul 2007 18:04:25 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Chuck Ebbert <76306.1226@...puserve.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [patch] i386: remove unnecessary code


* Oleg Nesterov <oleg@...sign.ru> wrote:

> I am really puzzled by set_fs(USER_DS) in setup_frame/setup_rt_frame.
> 
> How is it possible that current->addr_limit != USER_DS ? If this _is_ 
> possible, how can can we trust the result of access_ok() above?

hm, this is _ancient_ code (possibly dating back to the pharaohs). If we 
are in KERNEL_DS then we call do_signal() then we are most likely a 
kernel thread and regs->esp points to the kernel stack ... the result of 
which would be a quite spectacular crash anyway.

Patch below.

	Ingo

----------------------------->
Subject: [patch] i386: remove unnecessary code
From: Ingo Molnar <mingo@...e.hu>

Oleg Nesterov pointed out that the set_fs() calls in setup_frame()
and setup_rt_frame() were superfluous.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/i386/kernel/signal.c |    2 --
 1 file changed, 2 deletions(-)

Index: linux/arch/i386/kernel/signal.c
===================================================================
--- linux.orig/arch/i386/kernel/signal.c
+++ linux/arch/i386/kernel/signal.c
@@ -380,7 +380,6 @@ static int setup_frame(int sig, struct k
 	regs->edx = (unsigned long) 0;
 	regs->ecx = (unsigned long) 0;
 
-	set_fs(USER_DS);
 	regs->xds = __USER_DS;
 	regs->xes = __USER_DS;
 	regs->xss = __USER_DS;
@@ -474,7 +473,6 @@ static int setup_rt_frame(int sig, struc
 	regs->edx = (unsigned long) &frame->info;
 	regs->ecx = (unsigned long) &frame->uc;
 
-	set_fs(USER_DS);
 	regs->xds = __USER_DS;
 	regs->xes = __USER_DS;
 	regs->xss = __USER_DS;
-
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