linux-kernel - Re: [PATCH v2 0/4] futex: Drop ROBUST_LIST

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Message-ID: <875xlzl6lq.fsf@oldenburg.str.redhat.com>
Date: Tue, 28 Jan 2025 08:50:41 +0100
From: Florian Weimer <fweimer@...hat.com>
To: André Almeida <andrealmeid@...lia.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,  Ingo Molnar <mingo@...hat.com>,
  Peter Zijlstra <peterz@...radead.org>,  Darren Hart
 <dvhart@...radead.org>,  Davidlohr Bueso <dave@...olabs.net>,  Arnd
 Bergmann <arnd@...db.de>,  linux-kernel@...r.kernel.org,
  kernel-dev@...lia.com,  Vinicius Peixoto <vpeixoto@...amp.dev>
Subject: Re: [PATCH v2 0/4] futex: Drop ROBUST_LIST_LIMIT

* André Almeida:

> As requested by Peter at [1], this patchset drops the
> ROBUST_LIST_LIMIT. This is achieve by simply rewriting the processed
> list element ->next to point to the head->list address, destroying the
> linked list to avoid any circular list.

Doesn't this turn a robust mutex overwrite or a TCB overwrite into a
write-anything-anywhere primitive?  Furthermore, I'm not entirely sure
if this is entirely backwards-compatible.

Could you use the tortoise/hare approach instead?

Thanks,
Florian