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Date:   Tue, 16 Feb 2021 12:50:29 +0100
From:   Pavel Machek <pavel@ucw.cz>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Leon Romanovsky <leonro@mellanox.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 5.10 043/104] kasan: add explicit preconditions to
 kasan_report()
Message-ID: <20210216115029.GA25795@amd>
References: <20210215152719.459796636@linuxfoundation.org>
 <20210215152720.867409732@linuxfoundation.org>
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Hi!

> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>=20
> [ Upstream commit 49c6631d3b4f61a7b5bb0453a885a12bfa06ffd8 ]
>=20
> Patch series "kasan: Fix metadata detection for KASAN_HW_TAGS", v5.
>=20
> With the introduction of KASAN_HW_TAGS, kasan_report() currently assumes
> that every location in memory has valid metadata associated.  This is
> due to the fact that addr_has_metadata() returns always true.
>=20
> As a consequence of this, an invalid address (e.g.  NULL pointer
> address) passed to kasan_report() when KASAN_HW_TAGS is enabled, leads
> to a kernel panic.
=2E..
> This patch (of 2):
>=20
> With the introduction of KASAN_HW_TAGS, kasan_report() accesses the
> metadata only when addr_has_metadata() succeeds.
>=20
> Add a comment to make sure that the preconditions to the function are
> explicitly clarified.

As the other patch from the series is not applied, I don't believe we
need this in stable. Changelog does not make any sense with just
comment change cherry-picked...

Best regards,
								Pavel


> +++ b/include/linux/kasan.h
> @@ -196,6 +196,13 @@ void kasan_init_tags(void);
> =20
>  void *kasan_reset_tag(const void *addr);
> =20
> +/**
> + * kasan_report - print a report about a bad memory access detected by K=
ASAN
> + * @addr: address of the bad access
> + * @size: size of the bad access
> + * @is_write: whether the bad access is a write or a read
> + * @ip: instruction pointer for the accessibility check or the bad acces=
s itself
> + */
>  bool kasan_report(unsigned long addr, size_t size,
>  		bool is_write, unsigned long ip);
> =20

--=20
http://www.livejournal.com/~pavelmachek

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