linux-kernel - [PATCH 3.2 68/87] xtensa: don't use alternate signal stack on threads

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Message-ID: <lsq.1385387069.447655415@decadent.org.uk>
Date:	Mon, 25 Nov 2013 13:44:29 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Chris Zankel" <chris@...kel.net>,
	"Baruch Siach" <baruch@...s.co.il>,
	"Max Filippov" <jcmvbkbc@...il.com>
Subject: [PATCH 3.2 68/87] xtensa: don't use alternate signal stack on threads

3.2.53-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Baruch Siach <baruch@...s.co.il>

commit cba9a90053e3b7973eff4f1946f33032e98eeed5 upstream.

According to create_thread(3): "The new thread does not inherit the creating
thread's alternate signal stack". Since commit f9a3879a (Fix sigaltstack
corruption among cloned threads), current->sas_ss_size is set to 0 for cloned
processes sharing VM with their parent. Don't use the (nonexistent) alternate
signal stack in this case. This has been broken since commit 29c4dfd9 ([XTENSA]
Remove non-rt signal handling).

Fixes the SA_ONSTACK part of the nptl/tst-cancel20 test from uClibc.

Signed-off-by: Baruch Siach <baruch@...s.co.il>
Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
Signed-off-by: Chris Zankel <chris@...kel.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/xtensa/kernel/signal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/xtensa/kernel/signal.c
+++ b/arch/xtensa/kernel/signal.c
@@ -346,7 +346,7 @@ static void setup_frame(int sig, struct
 
 	sp = regs->areg[1];
 
-	if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! on_sig_stack(sp)) {
+	if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
 		sp = current->sas_ss_sp + current->sas_ss_size;
 	}
 

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