Commit af9ff786 authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Ingo Molnar
Browse files

x86: simplify stackprotector self-check 



Clean up the code by removing no longer needed code;
make sure the pda is updated and kept in sync

Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent aa92db14

include/asm-x86/pda.h

+1 −0
Original line number Diff line number Diff line
@@ -131,4 +131,5 @@ do { \ 


#define PDA_STACKOFFSET (5*8)



#define refresh_stack_canary() write_pda(stack_canary, current->stack_canary)

#endif

kernel/panic.c

+7 −22
Original line number Diff line number Diff line
@@ -328,37 +328,21 @@ EXPORT_SYMBOL(warn_on_slowpath); 
#ifndef GCC_HAS_SP

#warning You have selected the CONFIG_CC_STACKPROTECTOR option, but the gcc used does not support this.

#endif



static unsigned long __stack_check_testing;



/*

 * Self test function for the stack-protector feature.

 * This test requires that the local variable absolutely has

 * a stack slot, hence the barrier()s.

 * a stack slot.

 */

static noinline void __stack_chk_test_func(void)

{

	unsigned long foo;

	barrier();

	/*

	 * we need to make sure we're not about to clobber the return address,

	 * while real exploits do this, it's unhealthy on a running system.

	 * Besides, if we would, the test is already failed anyway so

	 * time to pull the emergency brake on it.

	 */

	if ((unsigned long)__builtin_return_address(0) ==

					*(((unsigned long *)&foo)+1)) {

		printk(KERN_ERR "No -fstack-protector-stack-frame!\n");

	}

#ifdef CONFIG_FRAME_POINTER

	/* We also don't want to clobber the frame pointer */

	if ((unsigned long)__builtin_return_address(0) ==

					*(((unsigned long *)&foo)+2)) {

		printk(KERN_ERR "No -fstack-protector-stack-frame!\n");

	}

#endif

	if (current->stack_canary != *(((unsigned long *)&foo)+1))

		printk(KERN_ERR "No -fstack-protector canary found\n");

	unsigned long dummy_buffer[64]; /* force gcc to use the canary */



	current->stack_canary = ~current->stack_canary;

	refresh_stack_canary();

	dummy_buffer[3] = 1; /* fool gcc into keeping the variable */

}



static int __stack_chk_test(void)
@@ -371,6 +355,7 @@ static int __stack_chk_test(void) 
		WARN_ON(1);

	};

	current->stack_canary = ~current->stack_canary;

	refresh_stack_canary();

	return 0;

}

/*