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

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Date:   Tue, 19 Jul 2022 12:50:35 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, yee.lee@...iatek.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        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>
Subject: Re: [PATCH v2 1/1] mm: kfence: apply kmemleak_ignore_phys on early
 allocated pool

On Sat, Jul 16, 2022 at 08:43:06PM +0200, Geert Uytterhoeven wrote:
> On Sat, Jul 16, 2022 at 1:33 AM Andrew Morton <akpm@...ux-foundation.org> wrote:
> > 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.
> 
> IIRC, I started seeing the issue with "[PATCH v4 3/4] mm:
> kmemleak: add rbtree and store physical address for objects
> allocated with PA" (i.e. commit 0c24e061196c21d5 ("mm: kmemleak:
> add rbtree and store physical address for objects allocated
> with PA")) of series "[PATCH v4 0/4] mm: kmemleak: store objects
> allocated with physical address separately and check when scan"
> (https://lore.kernel.org/all/20220611035551.1823303-1-patrick.wang.shcn@gmail.com),
> in an arm64 config that had enabled kfence.

Yes, I think it fixes 0c24e061196c21d5 since after that commit, the
kmemleak_free() no longer worked as expected on physically allocated
objects.

-- 
Catalin