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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: c55d240003 ("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>
This commit is contained in:
Arnd Bergmann 2017-01-11 15:56:44 +01:00 committed by Greg Kroah-Hartman
parent 4474f4c40a
commit 7a11a1d1b5
1 changed files with 6 additions and 1 deletions
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7
drivers/misc/lkdtm_bugs.c
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@ -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);
}