From 7a11a1d1b58873b2e5a6922dcdc23b6b339b14ba Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Wed, 11 Jan 2017 15:56:44 +0100 Subject: [PATCH] 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: c55d240003ae ("lkdtm: Prevent the compiler from optimising lkdtm_CORRUPT_STACK()") Signed-off-by: Arnd Bergmann Acked-by: Kees Cook Signed-off-by: Greg Kroah-Hartman --- drivers/misc/lkdtm_bugs.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/misc/lkdtm_bugs.c b/drivers/misc/lkdtm_bugs.c index 91edd0b55e5c..bb3bb8ef5f44 100644 --- a/drivers/misc/lkdtm_bugs.c +++ b/drivers/misc/lkdtm_bugs.c @@ -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); } -- 2.39.5