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Date:   Mon, 16 Jan 2017 21:23:35 +1100
From:   Michael Ellerman <>
To:     Arnd Bergmann <>, Kees Cook <>,
        Greg Kroah-Hartman <>
Cc:     Arnd Bergmann <>,
Subject: Re: [PATCH] lkdtm: hide stack overflow warning for corrupt-stack test

Arnd Bergmann <> writes:

> 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.

Heh, darn it.

I suspect this is an arms race we are eventually going to lose. At some
point we might have to switch to writing some of these in asm :/


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