linux-kernel - Re: [PATCH] futex: Initialize futex_phash

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Message-ID: <ca0dab04-7ccc-43e6-b5f3-7a739c867bc0@igalia.com>
Date: Mon, 23 Jun 2025 13:27:22 -0300
From: André Almeida <andrealmeid@...lia.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 linux-kernel@...r.kernel.org
Cc: Calvin Owens <calvin@...nvd.org>, Darren Hart <dvhart@...radead.org>,
 Davidlohr Bueso <dave@...olabs.net>, Ingo Molnar <mingo@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] futex: Initialize futex_phash_new during fork().

Em 23/06/2025 05:34, Sebastian Andrzej Siewior escreveu:
> During a hash resize operation the new private hash is stored in
> mm_struct::futex_phash_new if the current hash can not be immediately
> replaced.
> 
> The new hash must not be copied during fork() into the new task. Doing
> so will lead to a double-free of the memory by the two tasks.
> 
> Initialize the mm_struct::futex_phash_new during fork().
> 
> Reported-by: Calvin Owens <calvin@...nvd.org>
> Closes: https://lore.kernel.org/all/aFBQ8CBKmRzEqIfS@mozart.vkv.me/
> Tested-by: Calvin Owens <calvin@...nvd.org>
> Fixes: bd54df5ea7cad ("futex: Allow to resize the private local hash")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Reviewed-by: André Almeida <andrealmeid@...lia.com>