Could you clarify what exact behaviour Willem removed? On Tue, Oct 2, 2018 at 11:43 AM, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > On Tue, Oct 02, 2018 at 11:28:21AM -0700, Chenbo Feng wrote: >> On Tue, Oct 2, 2018 at 11:15 AM Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: >> > >> > Hi Chenbo, >> > >> > On Tue, Oct 02, 2018 at 10:45:58AM -0700, Chenbo Feng wrote: >> > > On Tue, Oct 2, 2018 at 3:51 AM Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: >> > [...] >> > > Do you mean the remain field will be zeroed when copying the >> > > xt_quota_info struct out of the kernel? I believe that is decided by >> > > the usersize defined in struct xt_match and this patch set it to the >> > > full struct size. So the whole xt_quota_info struct will be copied >> > > into userspace including the field stores the remaining quota. The >> > > userspace will not be aware of it if the ipatbles is not updated but >> > > it should not modify it as well. I have tested the behavior with >> > > net-next branch and it seems working. Am I missing something >> > > recently updated? >> > >> > Hm, I see, I overlook that your patch removes this: >> > >> > - .usersize = offsetof(struct xt_quota_info, master), >> > >> > BTW, is iptables -D command working with your patch? >> > >> > Telling this because if .usersize is removed, then IIRC userspace >> > compares this new remain field with userspace value and deletion will >> > break. >> > >> > Patch that I was referring before is this one from Willem: >> > >> > commit f32815d21d4d8287336fb9cef4d2d9e0866214c2 >> > Author: Willem de Bruijn <willemb@xxxxxxxxxx> >> > Date: Mon Jan 2 17:19:40 2017 -0500 >> > >> > xtables: add xt_match, xt_target and data copy_to_user functions >> > >> > xt_entry_target, xt_entry_match and their private data may contain >> > kernel data. >> > [...] >> > Private data is defined in xt_match and xt_target. All matches and >> > targets that maintain kernel data store this at the tail of their >> > private structure. Extend xt_match and xt_target with .usersize to >> > limit how many bytes of data are copied. The remainder is cleared. >> > >> > Let me know, thanks ! >> >> The delete operation is decided by the userspacesize defined in >> userspace ipatbles. I think it is unrelated to the usersize we talk >> about here. For old userspace iptables, the userspacesize is >> offsetof(struct xt_quota_info, master) so it will not compare the rest >> if the struct. And for new iptables we use offsetof(struct >> xt_quota_info, remain). Either way the userspace does not consider the >> remain field when comparing rules so we can do ipatbles rule deletion >> with or without specifying --remain option or even specify --remain to >> a wrong number. We decide to make it this way since the --remain field >> is changing all the time when there is network traffic going on and >> it's hard to compare the remaining quota for new ipatbles as well. > > Thanks for explaining and your patience. Patch looks good then. > > Thanks!
