Re: [RFC] kasan stack overflow warnings again: READ_ONCE(), typecheck()

[Arnd Bergmann]

On Wed, Feb 15, 2017 at 11:34 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Wed, Feb 15, 2017 at 10:18 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
>> On Wed, Feb 15, 2017 at 12:03 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:

> My current estimate is only a handful of patches to enable
> CONFIG_FRAME_WARN=3072 with a clean build, and maybe a few dozen
> more to get down to 2048 with gcc-7.0.1 (no idea for older versions).
>
> What I'm looking at now is this set of remaining warnings (>3072 bytes)
> and 24 other files >2048:

I now found that most of the remaining ones go away when I make
CONFIG_KMEMCHECK depend on !KASAN_EXTRA (from my earlier patch).
Presumably this definition:

static __always_inline void *__inline_memcpy(void *to, const void
*from, size_t n)
{
        unsigned long d0, d1, d2;
        asm volatile("rep ; movsl\n\t"
                     "testb $2,%b4\n\t"
                     "je 1f\n\t"
                     "movsw\n"
                     "1:\ttestb $1,%b4\n\t"
                     "je 2f\n\t"
                     "movsb\n"
                     "2:"
                     : "=&c" (d0), "=&D" (d1), "=&S" (d2)
                     : "0" (n / 4), "q" (n), "1" ((long)to), "2" ((long)from)
                     : "memory");
        return to;
}

is the culprit when building with -fsanitize-address-use-after-scope

     Arnd