Commit 7a11a1d1 authored Jan 11, 2017 by Arnd Bergmann Committed by Greg Kroah-Hartman Jan 19, 2017

lkdtm: hide stack overflow warning for corrupt-stack test

After the latest change to make sure the compiler actually does a memset,
it is now smart enough to flag the stack overflow at compile time,
at least with gcc-7.0:

drivers/misc/lkdtm_bugs.c: In function 'lkdtm_CORRUPT_STACK':
drivers/misc/lkdtm_bugs.c:88:144: warning: 'memset' writing 64 bytes into a region of size 8 overflows the destination [-Wstringop-overflow=]

To outsmart the compiler again, this moves the memset into a noinline
function where (for now) it doesn't see that we intentionally write
broken code here.

Fixes: c55d2400 ("lkdtm: Prevent the compiler from optimising lkdtm_CORRUPT_STACK()")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 4474f4c4

drivers/misc/lkdtm_bugs.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -80,12 +80,17 @@ void lkdtm_OVERFLOW(void)
		(void) recursive_loop(recur_count);
		}

		static noinline void __lkdtm_CORRUPT_STACK(void *stack)
		{
		memset(stack, 'a', 64);
		}

		noinline void lkdtm_CORRUPT_STACK(void)
		{
		/* Use default char array length that triggers stack protection. */
		char data[8];
		__lkdtm_CORRUPT_STACK(&data);

		memset((void *)data, 'a', 64);
		pr_info("Corrupted stack with '%16s'...\n", data);
		}