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 B645CC6FD19 for ; Thu, 16 Mar 2023 11:28:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229540AbjCPL2S (ORCPT ); Thu, 16 Mar 2023 07:28:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42658 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229735AbjCPL2S (ORCPT ); Thu, 16 Mar 2023 07:28:18 -0400 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:237:300::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85D4022DD6 for ; Thu, 16 Mar 2023 04:28:16 -0700 (PDT) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1pclmG-0006Vw-Hd; Thu, 16 Mar 2023 12:28:12 +0100 Date: Thu, 16 Mar 2023 12:28:12 +0100 From: Florian Westphal To: Kyuwon Shim Cc: pablo@netfilter.org, netfilter-devel@vger.kernel.org Subject: Re: [PATCH v2] ulogd2: Avoid use after free in unregister on global ulogd_fds linked list Message-ID: References: <1678233154187.35009@alliedtelesis.co.nz> <20230309012447.201582-1-kyuwon.shim@alliedtelesis.co.nz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230309012447.201582-1-kyuwon.shim@alliedtelesis.co.nz> Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Kyuwon Shim wrote: > The issue "core dumped" occurred from > ulogd_unregister_fd(). One of the processes is unlink > from list and remove, but some struct 'pi' values > freed without ulogd_unregister_fd(). > Unlink process needs to access the previous pointer > value of struct 'pi', but it was already freed. > > Therefore, the free() process moved location > after finishing all ulogd_unregister_fd(). I don't understand this patch. llist_for_each_entry_safe() doesn't dereference 'pi' after its free'd. Where does this deref happen? Can you share a backtrace? > + } > + } > + > + llist_for_each_entry(stack, &ulogd_pi_stacks, stack_list) { > + llist_for_each_entry_safe(pi, npi, &stack->list, list) { > free(pi); Perhaps there should be a 'llist_del' before pi gets free'd instead?