linux-kernel - Re: [PATCH v2 1/1] mm: kfence: apply kmemleak_ignore

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Message-Id: <20220715163305.e70c8542d5e7d96c5fd87185@linux-foundation.org>
Date:   Fri, 15 Jul 2022 16:33:05 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     yee.lee@...iatek.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "open list:KFENCE" <kasan-dev@...glegroups.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Marco Elver <elver@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v2 1/1] mm: kfence: apply kmemleak_ignore_phys on early
 allocated pool

On Fri, 15 Jul 2022 10:17:43 +0200 Geert Uytterhoeven <geert@...ux-m68k.org> wrote:

> On Tue, Jun 28, 2022 at 1:42 PM <yee.lee@...iatek.com> wrote:
> > From: Yee Lee <yee.lee@...iatek.com>
> >
> > This patch solves two issues.
> >
> > (1) The pool allocated by memblock needs to unregister from
> > kmemleak scanning. Apply kmemleak_ignore_phys to replace the
> > original kmemleak_free as its address now is stored in the phys tree.
> >
> > (2) The pool late allocated by page-alloc doesn't need to unregister.
> > Move out the freeing operation from its call path.
> >
> > Suggested-by: Catalin Marinas <catalin.marinas@....com>
> > Suggested-by: Marco Elver <elver@...gle.com>
> > Signed-off-by: Yee Lee <yee.lee@...iatek.com>
> 
> Thank you, this fixes the storm of
> 
>     BUG: KFENCE: invalid read in scan_block+0x78/0x130
>     BUG: KFENCE: use-after-free read in scan_block+0x78/0x130
>     BUG: KFENCE: out-of-bounds read in scan_block+0x78/0x130
> 
> messages I was seeing on arm64.

Thanks, but...

- It would be great if we could identify a Fixes: for this.

- This patch has been accused of crashing the kernel:

	https://lkml.kernel.org/r/YsFeUHkrFTQ7T51Q@xsang-OptiPlex-9020

  Do we think that report is bogus?