From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0176C433F5 for ; Wed, 18 May 2022 16:46:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240402AbiERQqd (ORCPT ); Wed, 18 May 2022 12:46:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50350 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240551AbiERQqa (ORCPT ); Wed, 18 May 2022 12:46:30 -0400 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:12e:520::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB3951400D for ; Wed, 18 May 2022 09:46:23 -0700 (PDT) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1nrMoX-0002Om-DX; Wed, 18 May 2022 18:46:21 +0200 Date: Wed, 18 May 2022 18:46:21 +0200 From: Florian Westphal To: Pablo Neira Ayuso Cc: netfilter-devel@vger.kernel.org, fw@strlen.de, fasnacht@protonmail.ch Subject: Re: [PATCH nf,v2] netfilter: nf_tables: disable bh to update per-cpu rnd_state Message-ID: <20220518164621.GH4316@breakpoint.cc> References: <20220518160022.224294-1-pablo@netfilter.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220518160022.224294-1-pablo@netfilter.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Pablo Neira Ayuso wrote: > bh might occur while updating per-cpu rnd_state from user context, > ie. local_out path. > > [233241.951068] BUG: using smp_processor_id() in preemptible [00000000] code: nginx/2725 > [233241.951220] caller is nft_ng_random_eval+0x24/0x54 [nft_numgen] > [233241.951225] CPU: 2 PID: 2725 Comm: nginx Tainted: G OE 5.16.0-0.bpo.4-amd64 #1 Debian 5.16.12-1~bpo11+1 > [233241.951227] Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021 > [233241.951228] Call Trace: > [233241.951231] > [233241.951233] dump_stack_lvl+0x48/0x5e > [233241.951236] check_preemption_disabled+0xde/0xe0 > [233241.951239] nft_ng_random_eval+0x24/0x54 [nft_numgen] > > Fixes: 6b2faee0ca91 ("netfilter: nft_meta: place prandom handling in a helper") > Fixes: 978d8f9055c3 ("netfilter: nft_numgen: add map lookups for numgen random operations") > Signed-off-by: Pablo Neira Ayuso > --- > v2: disable/enable bh > @Florian: your rand meta support is missing {disable,enable}_local_bh() I wonder if its better to just switch to get_random_u32() instead of prandom.