From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: [PATCH] net: make net namespace sysctls belong to container's owner Date: Mon, 08 Aug 2016 16:48:40 -0500 Message-ID: <87eg5zlyo7.fsf@x220.int.ebiederm.org> References: <20160802231926.GA8108@dtor-ws> <8737mfotnj.fsf@x220.int.ebiederm.org> Mime-Version: 1.0 Content-Type: text/plain Cc: "David S. Miller" , Al Viro , lkml , netdev To: Dmitry Torokhov Return-path: In-Reply-To: (Dmitry Torokhov's message of "Mon, 8 Aug 2016 14:54:45 -0700") Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Dmitry Torokhov writes: > On Mon, Aug 8, 2016 at 2:08 PM, Eric W. Biederman wrote: >> Dmitry Torokhov writes: >> >>> If net namespace is attached to a user namespace let's make container's >>> root owner of sysctls affecting said network namespace instead of global >>> root. >>> >>> This also allows us to clean up net_ctl_permissions() because we do not >>> need to fudge permissions anymore for the container's owner since it now >>> owns the objects in question. >> >> Acked-by: "Eric W. Biederman" >> >> Overall this seems reasonable. However I am not a fan of your error >> handling. >> >>> Signed-off-by: Dmitry Torokhov >>> --- >>> >>> This helps when running Android CTS in a container, but I think it makes >>> sense regardless. >> >>> +static void net_ctl_set_ownership(struct ctl_table_header *head, >>> + struct ctl_table *table, >>> + kuid_t *uid, kgid_t *gid) >>> +{ >>> + struct net *net = container_of(head->set, struct net, sysctls); >>> + >>> + *uid = make_kuid(net->user_ns, 0); >>> + if (!uid_valid(*uid)) >>> + *uid = GLOBAL_ROOT_UID; >>> + >>> + *gid = make_kgid(net->user_ns, 0); >>> + if (!gid_valid(*gid)) >>> + *gid = GLOBAL_ROOT_GID; >> >> This code should eiter be: >> *uid = make_kuid(net->user_ns, 0); >> *gid = make_kgid(net->user_ns, 0); >> >> Or it should be: >> tmp_uid = make_kuid(net->user_ns, 0); >> if (uid_valid(tmp_uid)) >> *uid = tmp_uid; >> >> tmp_gid = make_kgid(net->user_ns, 0); >> if (gid_valid(tmp_gid)) >> *gid = tmp_gid; >> >> It is just very fragile to assume to know what uid and gid >> would be if this code fails. >> >> As of v4.8-rc1 INVALID_UID and INVALID_GID can be set in inode->i_uid >> and inode->i_gid without causing horrible vfs confusion (making the >> first option viable), but I expect with the mention of Android you want >> to backport this so I will ask that you ask to implement the error >> handling that doesn't assume you know better than the generic code. >> >> If you don't have a better value to set something to it really should be >> left alone. > > OK, fair enough. I will adopt the 2nd option and will resubmit. I need > to also test without net namespaces support (my other change blows up > because we are getting half-initialized init_net structure when > namespaces are disabled). No rush. I will be out on vacation for the next couple of weeks. Eric