From: Thomas Gleixner <tglx@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Hao-Yu Yang <naup96721@gmail.com>,
mingo@redhat.com, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
David Hillenbrand <david@kernel.org>,
Eric Dumazet <edumazet@google.com>,
linux-mm@kvack.org
Subject: Re: [PATCH v2] futex: Use-after-free between futex_key_to_node_opt and vma_replace_policy
Date: Tue, 24 Mar 2026 17:36:42 +0100 [thread overview]
Message-ID: <87fr5pgp5x.ffs@tglx> (raw)
In-Reply-To: <20260324140019.GE3738010@noisy.programming.kicks-ass.net>
On Tue, Mar 24 2026 at 15:00, Peter Zijlstra wrote:
> On Mon, Mar 23, 2026 at 06:24:42PM +0100, Thomas Gleixner wrote:
> Not to mention we don't actually need any of that here, because:
>
>> Especially the writer side is required so that the proper memory
>> barriers are inserted for architectures with a weakly ordered memory
>> model.
>
> The vma->vm_policy thing is written under mmap_lock held for writing,
> and the futex consumer is a speculative read lock. Specifically the
> ordering is through the associated seqcount.
Duh. Yes.
> All that is really needed is to extend the lifetime of the mpol to the
> associated RCU period. Which is exactly what this patch does.
>
> Want me to go write up a better Changelog?
And a comment in the code explaining the RCU magic perhaps?
next prev parent reply other threads:[~2026-03-24 16:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-13 12:47 [PATCH v2] futex: Use-after-free between futex_key_to_node_opt and vma_replace_policy Hao-Yu Yang
2026-03-21 23:57 ` Hao-Yu Yang
2026-03-22 21:42 ` Thomas Gleixner
2026-03-23 17:24 ` Thomas Gleixner
2026-03-23 23:43 ` Hao-Yu Yang
2026-03-23 23:46 ` Hao-Yu Yang
2026-03-24 14:00 ` Peter Zijlstra
2026-03-24 15:54 ` Hao-Yu Yang
2026-03-24 16:36 ` Thomas Gleixner [this message]
2026-03-24 17:44 ` Peter Zijlstra
2026-03-24 19:25 ` Thomas Gleixner
2026-03-24 20:27 ` David Hildenbrand (Arm)
2026-03-25 15:14 ` Peter Zijlstra
2026-03-25 15:19 ` Eric Dumazet
2026-03-25 15:22 ` Peter Zijlstra
2026-03-25 15:24 ` David Hildenbrand (Arm)
2026-03-25 15:25 ` Eric Dumazet
2026-03-26 12:42 ` Hao-Yu Yang
2026-03-26 15:16 ` [tip: locking/urgent] futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy() tip-bot2 for Hao-Yu Yang
-- strict thread matches above, loose matches on Subject: below --
2026-03-13 12:39 [PATCH v2] futex: Use-after-free between futex_key_to_node_opt and vma_replace_policy Hao-Yu Yang
2026-03-13 12:44 ` Greg KH
2026-03-13 12:51 ` Hao-Yu Yang
2026-03-13 12:52 ` Peter Zijlstra
2026-03-13 12:55 ` Eric Dumazet
2026-03-13 13:01 ` Hao-Yu Yang
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