From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6DA8E1DE89A for ; Tue, 28 Jan 2025 07:50:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738050660; cv=none; b=NmCdO2FDehyFptvnQha4RL7xyQKn07rXXPxXOMu9fFm3oDyUl+gnIHYQat95zKNcc4Whp79LFqOH1p32Ftq0i5C4K+aNpi8Lk9TFET9XCwW5xpiyKWO3wLKY4vw/9CPkhkgaIhT0+lFY00AZq6hnR1f8mavoeaS8f/CIgnz5wog= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738050660; c=relaxed/simple; bh=3XynX1Rm99zseQP/US6cxOMQLcGd4yLNLRsb9mhkbSI=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=t4EYiHAoD79EMrYk7/WcwEFr7L4Zx+GcYAPc7OkPmM3oNBI5DXjQu94Mt1EROx2JRcHMjOZVldi8bBSJhb7xvdnXpZK2hQUZDxryWd/sE7bfCuP/4Mk7TJFIXOoUOCZTX7UMsY8orDc6pgaPUW45kQrCBUNE9TOYWrjVakEhOTg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=DyuIbsoC; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DyuIbsoC" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1738050657; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mQpItNrRsfFsHdyEG67VZFK14h4B1F1VrzXEUjDPJoo=; b=DyuIbsoCq2xWz9CCnSYEU7M1nDzfw8UmK0Ilt5GWuVFpepGr1loaYOlZm7Kl97HXYoF9q+ rDdkUIucXtEsNZzmeghuNpgvPoe93xy3eG609ZHYr+xH0byBbIGLlie0Uwfiy8bynYfCQs mBQyVBnJ+TQnjlAhun6JgsECR1mrd34= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-629-D3XL6xYRNS6Yjzu8QdJsYA-1; Tue, 28 Jan 2025 02:50:53 -0500 X-MC-Unique: D3XL6xYRNS6Yjzu8QdJsYA-1 X-Mimecast-MFC-AGG-ID: D3XL6xYRNS6Yjzu8QdJsYA Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B8A5C19560B3; Tue, 28 Jan 2025 07:50:49 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.2.16.12]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C37D619560AB; Tue, 28 Jan 2025 07:50:44 +0000 (UTC) From: Florian Weimer To: =?utf-8?Q?Andr=C3=A9?= Almeida Cc: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Darren Hart , Davidlohr Bueso , Arnd Bergmann , linux-kernel@vger.kernel.org, kernel-dev@igalia.com, Vinicius Peixoto Subject: Re: [PATCH v2 0/4] futex: Drop ROBUST_LIST_LIMIT In-Reply-To: <20250127202608.223864-1-andrealmeid@igalia.com> (=?utf-8?Q?=22Andr=C3=A9?= Almeida"'s message of "Mon, 27 Jan 2025 17:26:04 -0300") References: <20250127202608.223864-1-andrealmeid@igalia.com> Date: Tue, 28 Jan 2025 08:50:41 +0100 Message-ID: <875xlzl6lq.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 * Andr=C3=A9 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