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Date: Wed, 11 Feb 2009 13:09:27 +0000
From: David Howells <dhowells@...hat.com>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: dhowells@...hat.com, Serge Hallyn <serue@...ibm.com>,
LKML <linux-kernel@...r.kernel.org>,
Lee Schermerhorn <Lee.Schermerhorn@...com>
Subject: Re: [CRED bug?] 2.6.29-rc3 don't survive on stress workload
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
> > And can you give us your kernel config?
>
> attached.
Can you see the attached patch? You'll need to turn on
CONFIG_DEBUG_POISONED_PUT and you should keep CONFIG_DEBUG_SLAB on too.
I haven't tried compiling it for IA64, so the header change I made for that
may not compile.
David
---
From: David Howells <dhowells@...hat.com>
Subject: [PATCH] Attempt to catch atomic_dec_and_test() on freed and poisoned slab memory
Add an option to attempt to catch atomic_dec_and_test() on freed and poisoned
slab memory by complaining if the counter LSB is the poison value.
Signed-off-by: David Howells <dhowells@...hat.com>
---
arch/ia64/include/asm/atomic.h | 7 ++++++-
arch/x86/include/asm/atomic_32.h | 8 ++++++++
arch/x86/include/asm/atomic_64.h | 8 ++++++++
lib/Kconfig.debug | 10 ++++++++++
lib/Makefile | 1 +
lib/debug_poisoned_put.c | 39 ++++++++++++++++++++++++++++++++++++++
lib/dec_and_lock.c | 3 +++
7 files changed, 75 insertions(+), 1 deletions(-)
create mode 100644 lib/debug_poisoned_put.c
diff --git a/arch/ia64/include/asm/atomic.h b/arch/ia64/include/asm/atomic.h
index d37292b..b11ed7a 100644
--- a/arch/ia64/include/asm/atomic.h
+++ b/arch/ia64/include/asm/atomic.h
@@ -193,8 +193,13 @@ atomic64_add_negative (__s64 i, atomic64_t *v)
#define atomic64_dec_return(v) atomic64_sub_return(1, (v))
#define atomic64_inc_return(v) atomic64_add_return(1, (v))
+#ifdef CONFIG_DEBUG_POISONED_PUT
+extern void check_atomic_dec_and_test(atomic_t *v);
+#endif
+
#define atomic_sub_and_test(i,v) (atomic_sub_return((i), (v)) == 0)
-#define atomic_dec_and_test(v) (atomic_sub_return(1, (v)) == 0)
+#define atomic_dec_and_test(v) (check_atomic_dec_and_test(v), \
+ atomic_sub_return(1, (v)) == 0)
#define atomic_inc_and_test(v) (atomic_add_return(1, (v)) == 0)
#define atomic64_sub_and_test(i,v) (atomic64_sub_return((i), (v)) == 0)
#define atomic64_dec_and_test(v) (atomic64_sub_return(1, (v)) == 0)
diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h
index 85b46fb..b0b1a7c 100644
--- a/arch/x86/include/asm/atomic_32.h
+++ b/arch/x86/include/asm/atomic_32.h
@@ -101,6 +101,10 @@ static inline void atomic_dec(atomic_t *v)
: "+m" (v->counter));
}
+#ifdef CONFIG_DEBUG_POISONED_PUT
+extern void check_atomic_dec_and_test(atomic_t *v);
+#endif
+
/**
* atomic_dec_and_test - decrement and test
* @v: pointer of type atomic_t
@@ -113,6 +117,10 @@ static inline int atomic_dec_and_test(atomic_t *v)
{
unsigned char c;
+#ifdef CONFIG_DEBUG_POISONED_PUT
+ check_atomic_dec_and_test(v);
+#endif
+
asm volatile(LOCK_PREFIX "decl %0; sete %1"
: "+m" (v->counter), "=qm" (c)
: : "memory");
diff --git a/arch/x86/include/asm/atomic_64.h b/arch/x86/include/asm/atomic_64.h
index 8c21731..6a7f228 100644
--- a/arch/x86/include/asm/atomic_64.h
+++ b/arch/x86/include/asm/atomic_64.h
@@ -102,6 +102,10 @@ static inline void atomic_dec(atomic_t *v)
: "m" (v->counter));
}
+#ifdef CONFIG_DEBUG_POISONED_PUT
+extern void check_atomic_dec_and_test(atomic_t *v);
+#endif
+
/**
* atomic_dec_and_test - decrement and test
* @v: pointer of type atomic_t
@@ -114,6 +118,10 @@ static inline int atomic_dec_and_test(atomic_t *v)
{
unsigned char c;
+#ifdef CONFIG_DEBUG_POISONED_PUT
+ check_atomic_dec_and_test(v);
+#endif
+
asm volatile(LOCK_PREFIX "decl %0; sete %1"
: "=m" (v->counter), "=qm" (c)
: "m" (v->counter) : "memory");
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 29044f5..bb5801b 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -221,6 +221,16 @@ config TIMER_STATS
(it defaults to deactivated on bootup and will only be activated
if some application like powertop activates it explicitly).
+config DEBUG_POISONED_PUT
+ bool "Catch puts of already released memory"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, atomic_dec_and_test() will complain if it sees
+ what might be a poisoned value from a released slab object or a
+ counter already reduced to nothing. Note that this test cannot say
+ for certain that the value is in error - the value on the counter
+ might be completely legitimate.
+
config DEBUG_OBJECTS
bool "Debug object operations"
depends on DEBUG_KERNEL
diff --git a/lib/Makefile b/lib/Makefile
index 32b0e64..c47cc74 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -44,6 +44,7 @@ obj-$(CONFIG_PLIST) += plist.o
obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
obj-$(CONFIG_DEBUG_LIST) += list_debug.o
obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
+obj-$(CONFIG_DEBUG_POISONED_PUT) += debug_poisoned_put.o
ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
lib-y += dec_and_lock.o
diff --git a/lib/debug_poisoned_put.c b/lib/debug_poisoned_put.c
new file mode 100644
index 0000000..1e04325
--- /dev/null
+++ b/lib/debug_poisoned_put.c
@@ -0,0 +1,39 @@
+/* Deal with a poisoned atomic counter
+ *
+ * Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@...hat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/poison.h>
+#include <linux/module.h>
+#include <asm/atomic.h>
+
+/*
+ * Check to see if an atomic_dec_and_test() is being performed on released
+ * and poisoned memory
+ */
+extern void check_atomic_dec_and_test(atomic_t *v)
+{
+ int c = v->counter;
+
+ if (unlikely(
+#ifdef CONFIG_DEBUG_SLAB
+ c == (POISON_FREE << 24 |
+ POISON_FREE << 16 |
+ POISON_FREE << 8 |
+ POISON_FREE) ||
+#endif
+ c <= 0)) {
+ printk(KERN_WARNING "atomic_dec_and_test() of suspicious value."
+ " insn=%p addr=%p val=%d\n",
+ __builtin_return_address(0), v, c);
+ dump_stack();
+ }
+}
+EXPORT_SYMBOL(check_atomic_dec_and_test);
diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index a65c314..403c857 100644
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -20,6 +20,9 @@
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
#ifdef CONFIG_SMP
+#ifdef CONFIG_DEBUG_POISONED_PUT
+ check_atomic_dec_and_test(atomic);
+#endif
/* Subtract 1 from counter unless that drops it to 0 (ie. it was 1) */
if (atomic_add_unless(atomic, -1, 1))
return 0;
--
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