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Date: Tue, 20 Jan 2026 09:46:17 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Pimyn Girgis <pimyn@google.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, elver@google.com,
 dvyukov@google.com, glider@google.com, kasan-dev@googlegroups.com,
 stable@vger.kernel.org
Subject: Re: [PATCH] mm/kfence: randomize the freelist on initialization
Message-Id: <20260120094617.ed5a53e9ec40e8f0a91f8cb6@linux-foundation.org>
In-Reply-To: <20260120161510.3289089-1-pimyn@google.com>
References: <20260120161510.3289089-1-pimyn@google.com>
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On Tue, 20 Jan 2026 17:15:10 +0100 Pimyn Girgis <pimyn@google.com> wrote:

> Randomize the KFENCE freelist during pool initialization to make allocation
> patterns less predictable. This is achieved by shuffling the order in which
> metadata objects are added to the freelist using get_random_u32_below().
> 
> Additionally, ensure the error path correctly calculates the address range
> to be reset if initialization fails, as the address increment logic has
> been moved to a separate loop.
> 
> Cc: stable@vger.kernel.org
> Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")

It isn't clear (to me) what was wrong with 0ce20dd84089, nor why a
-stable backport is proposed.

Can we please have a full description of the current misbehavior?  What
are the worst-case userspace-visible effects of this flaw?