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
some time ago but was never merged:
http://marc.info/?l=linux-kernel&m=127144305403241&w=2
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: aneesh.kumar@linux.vnet.ibm.com
Cc: dzickus@redhat.com
Cc: bmr@redhat.com
Cc: jcastillo@redhat.com
Cc: jgh@redhat.com
Cc: minchan@kernel.org
Cc: tglx@linutronix.de
Cc: hannes@cmpxchg.org
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Daeseok Youn <daeseok.youn@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1410527779-8133-2-git-send-email-atomlin@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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 @@
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 @@
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 82ff3d6..118dca7 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -57,6 +57,7 @@
#include <linux/llist.h>
#include <linux/uidgid.h>
#include <linux/gfp.h>
+#include <linux/magic.h>
#include <asm/processor.h>
@@ -2638,6 +2639,7 @@
return (unsigned long)n - (unsigned long)end_of_stack(p);
}
#endif
+extern void set_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..5fc3fc7 100644
--- a/init/main.c
+++ b/init/main.c
@@ -508,6 +508,7 @@
* lockdep hash:
*/
lockdep_init();
+ set_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 9387ae8..ad64248 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -294,11 +294,18 @@
return 0;
}
+void set_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 @@
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 */
+ set_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 @@
i++;
}
- if ((current != &init_task &&
- *(end_of_stack(current)) != STACK_END_MAGIC)) {
+ if (*end_of_stack(current) != STACK_END_MAGIC) {
print_max_stack();
BUG();
}