From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) (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 DE4BB1591F0 for ; Sat, 5 Oct 2024 22:51:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=62.89.141.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728168717; cv=none; b=lslvlwnssXNNi5+QXQmWbiD4X/RExLKUyyEac+0tlv2b3xMw0hPMya5VEc6xGBhauYn70NUw4XBZ9COpJ4vWZsmPmQUBN06g2sAOkFfRAACTea79mLaQAQClNcMFaDNwloU15+QF2cYutdV8mDWIDZFIGADIDU0jajGWIYvvyNw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728168717; c=relaxed/simple; bh=PWbPk/91BWSgD7U6SQp6I1sP5y5aeq55/EMAIshOnm0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mpChP9udLtV8dp7CQXsxTx+DvysKGOhQru2N2+56jzPMaUEOkn4mrYPYQKsaWhkuKCBkzTDDcndVbNgwX/5WLgxgKjZTceTq/CSL/bray61lGpl1LTrmhs83vWyfYIbELvu/3dQ3lvWF94JsyIrJQFG1z30gGa3212L/neZ7iA4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk; spf=none smtp.mailfrom=ftp.linux.org.uk; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b=fWrfH4LK; arc=none smtp.client-ip=62.89.141.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="fWrfH4LK" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=FcEL1bmO1UcL2fj8S/pd+T8y+wocj4zjI1UZe+Ju31Q=; b=fWrfH4LKiJ+CJ19HhMyNZMuNnz DBrtdUJzRxPEkqkJi093DUYQKlkIj8fhxsegyVEXdKVl5jhTL8A7kkaUtIrY6rV/WVp8cB8zhUyoX JmOenxsy6zsETUYFKZLjAXyaNZUO6kVrD3847z+iWUuqrnUias2QbbixT8isZMppY3EToV1XCi8Tt rFnEomVXgrALeqbDjdcrNekAqP/qfBR3RU4XX+bnVSpny/84agiVZ5DKn3z8H50dCoICQJy97HQYZ mt19ab71rpaU59ZREi1M8gK/HIfNyE441ikKOPmuMrBGSS0L/or4ZEQkNyRE6Z7a4szg8szEAc+6/ NVZ3Wi0g==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.98 #2 (Red Hat Linux)) id 1sxDcu-00000001Bce-39zG; Sat, 05 Oct 2024 22:51:52 +0000 Date: Sat, 5 Oct 2024 23:51:52 +0100 From: Al Viro To: Linus Torvalds Cc: Christian Brauner , linux-fsdevel@vger.kernel.org, Thomas Gleixner , Jann Horn Subject: Re: [PATCH RFC 0/4] fs: port files to rcuref_long_t Message-ID: <20241005225152.GC4017910@ZenIV> References: <20241005-brauner-file-rcuref-v1-0-725d5e713c86@kernel.org> <20241005220100.GA4017910@ZenIV> <20241005222836.GB4017910@ZenIV> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro On Sat, Oct 05, 2024 at 03:43:16PM -0700, Linus Torvalds wrote: > Come on - the only possible reason for two billion files is a bad > user. Do we care what error return an attacker gets? No. We're not > talking about breaking existing programs. Umm... It can be a bad failure mode of a buggy program, really unpleasant to debug if the pile of references kept growing on stdin of that sucker, which just happens to be controlling tty of your login session; fork(2) starting to fail for everything that has it opened is not fun. That's really nit-picking though, since > So I don't think that's actually the important thing here. If we keep > it a 'long', I won't lose any sleep over it. ... exactly. > But using the rcuref code doesn't work (regardless of whether 32-bit > or 'long' ref), because of the memory ordering issues. *nod*