Commit d4311ff1 authored by Aaron Tomlin's avatar Aaron Tomlin Committed by Ingo Molnar
Browse files

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: default avatarAaron Tomlin <atomlin@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarMichael 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: default avatarIngo Molnar <mingo@kernel.org>
parent a15b12ac

arch/powerpc/mm/fault.c

+1 −2
Original line number Diff line number Diff line
@@ -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);

arch/x86/mm/fault.c

+1 −2
Original line number Diff line number Diff line
@@ -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;

include/linux/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -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>
@@ -2638,6 +2639,7 @@ static inline unsigned long stack_not_used(struct task_struct *p) 
	return (unsigned long)n - (unsigned long)end_of_stack(p);

}

#endif

extern void 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

init/main.c

+1 −0
Original line number Diff line number Diff line
@@ -508,6 +508,7 @@ asmlinkage __visible void __init start_kernel(void) 
	 * lockdep hash:

	 */

	lockdep_init();

	set_task_stack_end_magic(&init_task);

	smp_setup_processor_id();

	debug_objects_early_init();

kernel/fork.c

+9 −3
Original line number Diff line number Diff line
@@ -294,11 +294,18 @@ int __weak arch_dup_task_struct(struct task_struct *dst, 
	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 @@ 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 */

	set_task_stack_end_magic(tsk);



#ifdef CONFIG_CC_STACKPROTECTOR

	tsk->stack_canary = get_random_int();

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