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Date:   Sun, 25 Sep 2022 17:38:48 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Vlastimil Babka <vbabka@suse.cz>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        "Ruhl, Michael J" <michael.j.ruhl@intel.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
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        Eric Dumazet <edumazet@google.com>,
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Subject: Re: [PATCH v2 14/16] kasan: Remove ksize()-related tests
Message-ID: <202209251738.6A453BC008@keescook>
References: <20220923202822.2667581-1-keescook@chromium.org>
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 <CACT4Y+bg=j9VdteQwrJTNFF_t4EE5uDTMLj07+uMJ9-NcooXGQ@mail.gmail.com>
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On Sat, Sep 24, 2022 at 10:15:18AM +0200, Dmitry Vyukov wrote:
> On Fri, 23 Sept 2022 at 22:28, Kees Cook <keescook@chromium.org> wrote:
> >
> > In preparation for no longer unpoisoning in ksize(), remove the behavioral
> > self-tests for ksize().
> >
> > [...]
> > -/* Check that ksize() makes the whole object accessible. */
> > -static void ksize_unpoisons_memory(struct kunit *test)
> > -{
> > -       char *ptr;
> > -       size_t size = 123, real_size;
> > -
> > -       ptr = kmalloc(size, GFP_KERNEL);
> > -       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> > -       real_size = ksize(ptr);
> > -
> > -       OPTIMIZER_HIDE_VAR(ptr);
> > -
> > -       /* This access shouldn't trigger a KASAN report. */
>  > -       ptr[size] = 'x';
> 
> I would rather keep the tests and update to the new behavior. We had
> bugs in ksize, we need test coverage.
> I assume ptr[size] access must now produce an error even after ksize.

Good point on all these! I'll respin.

-- 
Kees Cook