linux-kernel - Re: [PATCH 5.10 043/104] kasan: add explicit preconditions to kasan

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Date:   Wed, 17 Feb 2021 10:26:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Pavel Machek <pavel@....cz>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 043/104] kasan: add explicit preconditions to
 kasan_report()

On Tue, Feb 16, 2021 at 12:50:29PM +0100, Pavel Machek wrote:
> Hi!
> 
> > From: Vincenzo Frascino <vincenzo.frascino@....com>
> > 
> > [ Upstream commit 49c6631d3b4f61a7b5bb0453a885a12bfa06ffd8 ]
> > 
> > Patch series "kasan: Fix metadata detection for KASAN_HW_TAGS", v5.
> > 
> > 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.
> > 
> > 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.
> ...
> > This patch (of 2):
> > 
> > With the introduction of KASAN_HW_TAGS, kasan_report() accesses the
> > metadata only when addr_has_metadata() succeeds.
> > 
> > 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...

Good point, now dropped, the AUTOBOT triggered off of the changelog text
which is nice and scary :)

greg k-h