linux-kernel - Re: [PATCH] mm/kasan: Don't vfree() nonexistent vm

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Message-Id: <20180522140305.5e0f8c62dcc2d735ed4ee84c@linux-foundation.org>
Date:   Tue, 22 May 2018 14:03:05 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Paul Menzel <pmenzel+linux-kasan-dev@...gen.mpg.de>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm/kasan: Don't vfree() nonexistent vm_area.

On Tue, 22 May 2018 19:44:06 +0300 Andrey Ryabinin <aryabinin@...tuozzo.com> wrote:

> > Obviously we can't call vfree() to free memory that wasn't allocated via
> > vmalloc(). Use find_vm_area() to see if we can call vfree().
> > 
> > Unfortunately it's a bit tricky to properly unmap and free shadow allocated
> > during boot, so we'll have to keep it. If memory will come online again
> > that shadow will be reused.
> > 
> > Fixes: fa69b5989bb0 ("mm/kasan: add support for memory hotplug")
> > Reported-by: Paul Menzel <pmenzel+linux-kasan-dev@...gen.mpg.de>
> > Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> > Cc: <stable@...r.kernel.org>
> > ---
> 
> This seems stuck in -mm. Andrew, can we proceed?

OK.

Should there be a code comment explaining the situation that Matthew
asked about?  It's rather obscure.