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SubjectRe: Long standing bug in alternate stack handling
On Wed, Feb 21, 2001 at 11:02:17PM +0100, Christian Ehrhardt wrote:


[ 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

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