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From: "Christian Ehrhardt" <ehrhardt@mathematik.uni-ulm.de>
Date: Thu, 26 Apr 2001 00:13:47 +0200
To: linux-kernel@vger.kernel.org
Cc: alan@redhat.com
Subject: Re: Long standing bug in alternate stack handling
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In-Reply-To: <20010221220217.29816.qmail@theseus.mathematik.uni-ulm.de>; from ehrhardt@mathematik.uni-ulm.de on Wed, Feb 21, 2001 at 11:02:17PM +0100
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On Wed, Feb 21, 2001 at 11:02:17PM +0100, Christian Ehrhardt wrote:

Hi,

[ Sorry for the follow up on my own post ]

> If a signal handler is registered with the SA_ONSTACK flag the
> kernel will try to execute the signal handler on the alternate
> stack even if no such stack is registered.

Here's a simple patch for i386. Please consider it for inclusion.
Posix explicitly requires the behaviour implemented by this patch.


--- arch/i386/kernel/signal.c.old	Mon Sep 25 22:10:28 2000
+++ arch/i386/kernel/signal.c	Sun Apr 22 16:04:47 2001
@@ -371,7 +371,7 @@
 
 	/* This is the X/Open sanctioned signal stack switching.  */
 	if (ka->sa.sa_flags & SA_ONSTACK) {
-		if (! on_sig_stack(esp))
+		if (sas_ss_flags(esp) == 0)
 			esp = current->sas_ss_sp + current->sas_ss_size;
 	}
 
NOTE: As far as I can tell all archs are affected by this bug.

   best regards   Christian Ehrhardt

-- 
THAT'S ALL FOLKS!
-
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