linux-kernel - Re: next: x86_64: kunit test crashed and kernel panic

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Date:   Thu, 16 Feb 2023 19:58:55 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Marco Elver <elver@...gle.com>,
        Jakub Jelinek <jakub@...hat.com>,
        Peter Collingbourne <pcc@...gle.com>
Cc:     kasan-dev <kasan-dev@...glegroups.com>,
        open list <linux-kernel@...r.kernel.org>,
        kunit-dev@...glegroups.com, lkft-triage@...ts.linaro.org,
        regressions@...ts.linux.dev,
        Anders Roxell <anders.roxell@...aro.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: next: x86_64: kunit test crashed and kernel panic

>
> > <4>[   38.796558]  ? kmalloc_memmove_negative_size+0xeb/0x1f0
> > <4>[   38.797376]  ? __pfx_kmalloc_memmove_negative_size+0x10/0x10
>
> Most certainly kmalloc_memmove_negative_size() is related.
> Looks like we fail to intercept the call to memmove() in this test,
> passing -2 to the actual __memmove().

This was introduced by 69d4c0d321869 ("entry, kasan, x86: Disallow
overriding mem*() functions")

There's Marco's "kasan: Emit different calls for instrumentable
memintrinsics", but it doesn't fix the problem for me (looking
closer...), and GCC support is still not there, right?

Failing to intercept memcpy/memset/memmove should normally result in
false negatives, but kmalloc_memmove_negative_size() makes a strong
assumption that KASAN will catch and prevent memmove(dst, src, -2).