Date:   Wed, 15 Mar 2023 12:54:25 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Marco Elver <elver@google.com>
Cc:     Muchun Song <songmuchun@bytedance.com>, glider@google.com,
        dvyukov@google.com, jannh@google.com, sjpark@amazon.de,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, muchun.song@linux.dev
Subject: Re: [PATCH] mm: kfence: fix using kfence_metadata without
 initialization in show_object()
Message-Id: <20230315125425.70a22d32cf46b23d249775ec@linux-foundation.org>
In-Reply-To: <CANpmjNMxDT+AHBZra9ryhm6aw+WqBsdJ_SKdcdZr6CBsh97LyQ@mail.gmail.com>
References: <20230315034441.44321-1-songmuchun@bytedance.com>
        <CANpmjNMxDT+AHBZra9ryhm6aw+WqBsdJ_SKdcdZr6CBsh97LyQ@mail.gmail.com>
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On Wed, 15 Mar 2023 09:07:40 +0100 Marco Elver <elver@google.com> wrote:

> On Wed, 15 Mar 2023 at 04:45, Muchun Song <songmuchun@bytedance.com> wrote:
> >
> > The variable kfence_metadata is initialized in kfence_init_pool(), then, it is
> > not initialized if kfence is disabled after booting. In this case, kfence_metadata
> > will be used (e.g. ->lock and ->state fields) without initialization when reading
> > /sys/kernel/debug/kfence/objects. There will be a warning if you enable
> > CONFIG_DEBUG_SPINLOCK. Fix it by creating debugfs files when necessary.
> >
> > Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> 
> Tested-by: Marco Elver <elver@google.com>
> Reviewed-by: Marco Elver <elver@google.com>

Thanks, I'll add cc:stable to this.

I assume the warning is the only known adverse effect of this bug?