From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xin Long Subject: Re: [PATCH net] net: sched: fix NULL pointer dereference when action calls some targets Date: Thu, 17 Aug 2017 19:45:45 +1200 Message-ID: References: <0fa9a53725dd661571461cf283ec88cf15f4b139.1501932907.git.lucien.xin@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: network dev , David Miller , netfilter-devel@vger.kernel.org, Jamal Hadi Salim To: Cong Wang Return-path: In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org On Thu, Aug 17, 2017 at 5:57 PM, Cong Wang wrote: > On Wed, Aug 16, 2017 at 1:39 AM, Xin Long wrote: >> On Wed, Aug 9, 2017 at 7:33 AM, Cong Wang wrote: >>> On Mon, Aug 7, 2017 at 7:33 PM, Xin Long wrote: >>>> On Tue, Aug 8, 2017 at 9:15 AM, Cong Wang wrote: >>>>> This looks like a completely API burden? >>>> netfilter xt targets are not really compatible with netsched action. >>>> I've got to say, the patch is just a way to make checkentry return >>>> false and avoid panic. like [1] said >>> >>> I don't doubt you fix a crash, I am thinking if we can >>> "fix" the API instead of fixing the caller. >> Hi, Cong, >> >> For now, I don't think it's possible to change APIs or some of their targets >> for the panic caused by action xt calling. >> >> The common way should be fixed in net_sched side. >> >> Given that the issue is very easy to triggered, >> let's wait for netfilter's replies for another few days, >> otherwise I will repost the fix, agree ? > > Yeah, no objections from me. > > By the way, do you know how other callers of this API > use 'entryinfo'? Do they pass the address of the struct > on stack too? afaik, two places: 1. translate_table -> find_check_entry -> check_target -> xt_check_target most iptables operations go there and .entryinfo is set in check_target with struct ipt_entry *e, which is an iptable rule, so can't be NULL. (as well as ip6table in netfilter/ip6_tables.c ) 2. nft_target_init -> xt_check_target, where nft_target_set_tgchk_param does the exact thing to set .entryinfo with a local varible union nft_entry e: union nft_entry { struct ipt_entry e4; struct ip6t_entry e6; struct ebt_entry ebt; struct arpt_entry arp; }; case 2 is actually what nft does to use xt targets, so net/sched action should do the same.