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Message-Id: <1410204197-31204-2-git-send-email-atomlin@redhat.com>
Date: Mon, 8 Sep 2014 20:23:15 +0100
From: Aaron Tomlin <atomlin@...hat.com>
To: peterz@...radead.org
Cc: mingo@...hat.com, dzickus@...hat.com, bmr@...hat.com,
jcastillo@...hat.com, atomlin@...hat.com, oleg@...hat.com,
pzijlstr@...hat.com, riel@...hat.com, linux-kernel@...r.kernel.org,
tglx@...utronix.de, x86@...nel.org, rostedt@...dmis.org,
hannes@...xchg.org, aneesh.kumar@...ux.vnet.ibm.com,
akpm@...ux-foundation.org, akpm@...gle.com,
linuxppc-dev@...ts.ozlabs.org, minchan@...nel.org
Subject: [PATCH 1/3] init/main.c: Give init_task a canary
Tasks get their end of stack set to STACK_END_MAGIC with the
aim to catch stack overruns. Currently this feature does not
apply to init_task. This patch removes this restriction.
Note that a similar patch was posted by Prarit Bhargava [1]
some time ago but was never merged.
[1]: http://marc.info/?l=linux-kernel&m=127144305403241&w=2
Signed-off-by: Aaron Tomlin <atomlin@...hat.com>
---
arch/powerpc/mm/fault.c | 3 +--
arch/x86/mm/fault.c | 3 +--
include/linux/sched.h | 2 ++
init/main.c | 1 +
kernel/fork.c | 12 +++++++++---
kernel/trace/trace_stack.c | 4 +---
6 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 51ab9e7..35d0760c 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -30,7 +30,6 @@
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/perf_event.h>
-#include <linux/magic.h>
#include <linux/ratelimit.h>
#include <linux/context_tracking.h>
@@ -538,7 +537,7 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
regs->nip);
stackend = end_of_stack(current);
- if (current != &init_task && *stackend != STACK_END_MAGIC)
+ if (*stackend != STACK_END_MAGIC)
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
die("Kernel access of bad area", regs, sig);
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index a241946..bc23a70 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -3,7 +3,6 @@
* Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
* Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
*/
-#include <linux/magic.h> /* STACK_END_MAGIC */
#include <linux/sched.h> /* test_thread_flag(), ... */
#include <linux/kdebug.h> /* oops_begin/end, ... */
#include <linux/module.h> /* search_exception_table */
@@ -710,7 +709,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
show_fault_oops(regs, error_code, address);
stackend = end_of_stack(tsk);
- if (tsk != &init_task && *stackend != STACK_END_MAGIC)
+ if (*stackend != STACK_END_MAGIC)
printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
tsk->thread.cr2 = address;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5c2c885..4dee9d7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -57,6 +57,7 @@ struct sched_param {
#include <linux/llist.h>
#include <linux/uidgid.h>
#include <linux/gfp.h>
+#include <linux/magic.h>
#include <asm/processor.h>
@@ -2636,6 +2637,7 @@ static inline unsigned long stack_not_used(struct task_struct *p)
return (unsigned long)n - (unsigned long)end_of_stack(p);
}
#endif
+extern void task_stack_end_magic(struct task_struct *tsk);
/* set thread flags in other task's structures
* - see asm/thread_info.h for TIF_xxxx flags available
diff --git a/init/main.c b/init/main.c
index bb1aed9..bcdabf3a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -508,6 +508,7 @@ asmlinkage __visible void __init start_kernel(void)
* lockdep hash:
*/
lockdep_init();
+ task_stack_end_magic(&init_task);
smp_setup_processor_id();
debug_objects_early_init();
diff --git a/kernel/fork.c b/kernel/fork.c
index 0cf9cdb..67cb1e3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -294,11 +294,18 @@ int __weak arch_dup_task_struct(struct task_struct *dst,
return 0;
}
+void task_stack_end_magic(struct task_struct *tsk)
+{
+ unsigned long *stackend;
+
+ stackend = end_of_stack(tsk);
+ *stackend = STACK_END_MAGIC; /* for overflow detection */
+}
+
static struct task_struct *dup_task_struct(struct task_struct *orig)
{
struct task_struct *tsk;
struct thread_info *ti;
- unsigned long *stackend;
int node = tsk_fork_get_node(orig);
int err;
@@ -328,8 +335,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
setup_thread_stack(tsk, orig);
clear_user_return_notifier(tsk);
clear_tsk_need_resched(tsk);
- stackend = end_of_stack(tsk);
- *stackend = STACK_END_MAGIC; /* for overflow detection */
+ task_stack_end_magic(tsk);
#ifdef CONFIG_CC_STACKPROTECTOR
tsk->stack_canary = get_random_int();
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 8a4e5cb..1636e41 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -13,7 +13,6 @@
#include <linux/sysctl.h>
#include <linux/init.h>
#include <linux/fs.h>
-#include <linux/magic.h>
#include <asm/setup.h>
@@ -171,8 +170,7 @@ check_stack(unsigned long ip, unsigned long *stack)
i++;
}
- if ((current != &init_task &&
- *(end_of_stack(current)) != STACK_END_MAGIC)) {
+ if (*end_of_stack(current) != STACK_END_MAGIC) {
print_max_stack();
BUG();
}
--
1.9.3
--
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