On Wed, Apr 17, 2024 at 3:02 PM Julian Anastasov <ja@xxxxxx> wrote: > > > Hello, Dear Julian, > > On Tue, 16 Apr 2024, Alexander Mikhalitsyn wrote: > > > Let's make all IPVS sysctls visible and RO even when > > network namespace is owned by non-initial user namespace. > > > > Let's make a few sysctls to be writable: > > - conntrack > > - conn_reuse_mode > > - expire_nodest_conn > > - expire_quiescent_template > > > > I'm trying to be conservative with this to prevent > > introducing any security issues in there. Maybe, > > we can allow more sysctls to be writable, but let's > > do this on-demand and when we see real use-case. > > > > This list of sysctls was chosen because I can't > > see any security risks allowing them and also > > Kubernetes uses [2] these specific sysctls. > > > > This patch is motivated by user request in the LXC > > project [1]. > > > > [1] https://github.com/lxc/lxc/issues/4278 > > [2] https://github.com/kubernetes/kubernetes/blob/b722d017a34b300a2284b890448e5a605f21d01e/pkg/proxy/ipvs/proxier.go#L103 > > > > Cc: Stéphane Graber <stgraber@xxxxxxxxxxxx> > > Cc: Christian Brauner <brauner@xxxxxxxxxx> > > Cc: Julian Anastasov <ja@xxxxxx> > > Cc: Simon Horman <horms@xxxxxxxxxxxx> > > Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> > > Cc: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx> > > Cc: Florian Westphal <fw@xxxxxxxxx> > > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx> > > --- > > net/netfilter/ipvs/ip_vs_ctl.c | 18 +++++++++++++++--- > > 1 file changed, 15 insertions(+), 3 deletions(-) > > > > diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c > > index 143a341bbc0a..92a818c2f783 100644 > > --- a/net/netfilter/ipvs/ip_vs_ctl.c > > +++ b/net/netfilter/ipvs/ip_vs_ctl.c > > @@ -4285,10 +4285,22 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs) > > As the list of privileged vars is short I prefer > to use a bool and to make only some vars read-only: > > bool unpriv = false; > > > if (tbl == NULL) > > return -ENOMEM; > > > > - /* Don't export sysctls to unprivileged users */ > > + /* Let's show all sysctls in non-init user namespace-owned > > + * net namespaces, but make them read-only. > > + * > > + * Allow only a few specific sysctls to be writable. > > + */ > > if (net->user_ns != &init_user_ns) { > > Here we should just set: unpriv = true; > > > - tbl[0].procname = NULL; > > - ctl_table_size = 0; > > + for (idx = 0; idx < ARRAY_SIZE(vs_vars); idx++) { > > + if (!tbl[idx].procname) > > + continue; > > + > > + if (!((strcmp(tbl[idx].procname, "conntrack") == 0) || > > + (strcmp(tbl[idx].procname, "conn_reuse_mode") == 0) || > > + (strcmp(tbl[idx].procname, "expire_nodest_conn") == 0) || > > + (strcmp(tbl[idx].procname, "expire_quiescent_template") == 0))) > > + tbl[idx].mode = 0444; > > + } > > } > > } else > > tbl = vs_vars; > > And below at every place to use: > > if (unpriv) > tbl[idx].mode = 0444; > > for the following 4 privileged sysctl vars: > > - sync_qlen_max: > - allocates messages in kernel context > - this needs better tunning in another patch > > - sync_sock_size: > - allocates messages in kernel context > > - run_estimation: > - for now, better init ns to decide if to use est stats > > - est_nice: > - for now, better init ns to decide the value > > - debug_level: > - already set to 0444 > > I.e. these vars allocate resources (mem, CPU) without > proper control, so for now we will just copy them from init ns > without allowing writing. And they are vars that are not tuned > often. Also we do not know which netns is supposed to be the > privileged one, some solutions move all devices out of init_net, > so we can not decide where to use lower limits. I agree. I have also decided to forbid "est_cpulist" for unprivileged users. > > OTOH, "amemthresh" is not privileged but needs single READ_ONCE > for sysctl_amemthresh in update_defense_level() due to the possible > div by zero if we allow writing to anyone, eg.: > > int amemthresh = max(READ_ONCE(ipvs->sysctl_amemthresh), 0); > ... > nomem = availmem < amemthresh; > ... use only amemthresh > > All other vars can be writable. Have fixed this and sent it as a separate patch! ;-) Thanks a lot for such a quick review! Kind regards, Alex > > Regards > > -- > Julian Anastasov <ja@xxxxxx>
