From: Greg Kroah-Hartman <gregkh@suse.de>
Date: Thu, 10 Dec 2009 19:05:40 +0000 (-0800)
Subject: start .27 queue
X-Git-Tag: v2.6.31.8~5
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b22d7a3fc2297f81d4b4be50583ad47577868569;p=thirdparty%2Fkernel%2Fstable-queue.git

start .27 queue
---

diff --git a/queue-2.6.27/series b/queue-2.6.27/series
new file mode 100644
index 00000000000..0b37ab67df4
--- /dev/null
+++ b/queue-2.6.27/series
@@ -0,0 +1 @@
+signal-fix-alternate-signal-stack-check.patch
diff --git a/queue-2.6.27/signal-fix-alternate-signal-stack-check.patch b/queue-2.6.27/signal-fix-alternate-signal-stack-check.patch
new file mode 100644
index 00000000000..03764fd2103
--- /dev/null
+++ b/queue-2.6.27/signal-fix-alternate-signal-stack-check.patch
@@ -0,0 +1,87 @@
+From 2a855dd01bc1539111adb7233f587c5c468732ac Mon Sep 17 00:00:00 2001
+From: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
+Date: Sun, 25 Oct 2009 15:37:58 +0100
+Subject: signal: Fix alternate signal stack check
+
+From: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
+
+commit 2a855dd01bc1539111adb7233f587c5c468732ac upstream.
+
+All architectures in the kernel increment/decrement the stack pointer
+before storing values on the stack.
+
+On architectures which have the stack grow down sas_ss_sp == sp is not
+on the alternate signal stack while sas_ss_sp + sas_ss_size == sp is
+on the alternate signal stack.
+
+On architectures which have the stack grow up sas_ss_sp == sp is on
+the alternate signal stack while sas_ss_sp + sas_ss_size == sp is not
+on the alternate signal stack.
+
+The current implementation fails for architectures which have the
+stack grow down on the corner case where sas_ss_sp == sp.This was
+reported as Debian bug #544905 on AMD64.
+Simplified test case: http://download.breakpoint.cc/tc-sig-stack.c
+
+The test case creates the following stack scenario:
+   0xn0300	stack top
+   0xn0200	alt stack pointer top (when switching to alt stack)
+   0xn01ff	alt stack end
+   0xn0100	alt stack start == stack pointer
+
+If the signal is sent the stack pointer is pointing to the base
+address of the alt stack and the kernel erroneously decides that it
+has already switched to the alternate stack because of the current
+check for "sp - sas_ss_sp < sas_ss_size"
+
+On parisc (stack grows up) the scenario would be:
+   0xn0200	stack pointer
+   0xn01ff	alt stack end
+   0xn0100	alt stack start = alt stack pointer base
+   		    	  	  (when switching to alt stack)
+   0xn0000	stack base
+
+This is handled correctly by the current implementation.
+
+[ tglx: Modified for archs which have the stack grow up (parisc) which
+  	would fail with the correct implementation for stack grows
+  	down. Added a check for sp >= current->sas_ss_sp which is
+  	strictly not necessary but makes the code symetric for both
+  	variants ]
+
+Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
+Cc: Oleg Nesterov <oleg@redhat.com>
+Cc: Roland McGrath <roland@redhat.com>
+Cc: Kyle McMartin <kyle@mcmartin.ca>
+LKML-Reference: <20091025143758.GA6653@Chamillionaire.breakpoint.cc>
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
+
+---
+ include/linux/sched.h |   13 ++++++++++---
+ 1 file changed, 10 insertions(+), 3 deletions(-)
+
+--- a/include/linux/sched.h
++++ b/include/linux/sched.h
+@@ -1803,11 +1803,18 @@ static inline int is_si_special(const st
+ 	return info <= SEND_SIG_FORCED;
+ }
+ 
+-/* True if we are on the alternate signal stack.  */
+-
++/*
++ * True if we are on the alternate signal stack.
++ */
+ static inline int on_sig_stack(unsigned long sp)
+ {
+-	return (sp - current->sas_ss_sp < current->sas_ss_size);
++#ifdef CONFIG_STACK_GROWSUP
++	return sp >= current->sas_ss_sp &&
++		sp - current->sas_ss_sp < current->sas_ss_size;
++#else
++	return sp > current->sas_ss_sp &&
++		sp - current->sas_ss_sp <= current->sas_ss_size;
++#endif
+ }
+ 
+ static inline int sas_ss_flags(unsigned long sp)