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.
