[PATCH net-next v2 1/2] ipvs: add READ_ONCE barrier for ipvs->sysctl_amemthresh

[PATCH net-next v2 1/2] ipvs: add READ_ONCE barrier for ipvs->sysctl_amemthresh

[Alexander Mikhalitsyn]

Cc: Julian Anastasov <ja@ssi.bg>
Cc: Simon Horman <horms@verge.net.au>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
Cc: Florian Westphal <fw@strlen.de>
Suggested-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 143a341bbc0a..daa62b8b2dd1 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -94,6 +94,7 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 {
 	struct sysinfo i;
 	int availmem;
+	int amemthresh;
 	int nomem;
 	int to_change = -1;
 
@@ -105,7 +106,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 	/* si_swapinfo(&i); */
 	/* availmem = availmem - (i.totalswap - i.freeswap); */
 
-	nomem = (availmem < ipvs->sysctl_amemthresh);
+	amemthresh = max(READ_ONCE(ipvs->sysctl_amemthresh), 0);
+	nomem = (availmem < amemthresh);
 
 	local_bh_disable();
 
@@ -146,8 +148,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 	case 1:
 		if (nomem) {
 			ipvs->drop_rate = ipvs->drop_counter
-				= ipvs->sysctl_amemthresh /
-				(ipvs->sysctl_amemthresh-availmem);
+				= amemthresh /
+				(amemthresh-availmem);
 			ipvs->sysctl_drop_packet = 2;
 		} else {
 			ipvs->drop_rate = 0;
@@ -156,8 +158,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
 	case 2:
 		if (nomem) {
 			ipvs->drop_rate = ipvs->drop_counter
-				= ipvs->sysctl_amemthresh /
-				(ipvs->sysctl_amemthresh-availmem);
+				= amemthresh /
+				(amemthresh-availmem);
 		} else {
 			ipvs->drop_rate = 0;
 			ipvs->sysctl_drop_packet = 1;
-- 
2.34.1

[PATCH net-next v2 2/2] ipvs: allow some sysctls in non-init user namespaces

[Alexander Mikhalitsyn]

Let's make all IPVS sysctls writtable even when
network namespace is owned by non-initial user namespace.

Let's make a few sysctls to be read-only for non-privileged users:
- sync_qlen_max
- sync_sock_size
- run_estimation
- est_cpulist
- est_nice

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 patch is motivated by user request in the LXC
project [1]. Having this can help with running some
Kubernetes [2] or Docker Swarm [3] workloads inside the system
containers.

[1] https://github.com/lxc/lxc/issues/4278
[2] https://github.com/kubernetes/kubernetes/blob/b722d017a34b300a2284b890448e5a605f21d01e/pkg/proxy/ipvs/proxier.go#L103
[3] https://github.com/moby/libnetwork/blob/3797618f9a38372e8107d8c06f6ae199e1133ae8/osl/namespace_linux.go#L682

Cc: Stéphane Graber <stgraber@stgraber.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: Simon Horman <horms@verge.net.au>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index daa62b8b2dd1..f84f091626ef 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -4272,6 +4272,7 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
 	struct ctl_table *tbl;
 	int idx, ret;
 	size_t ctl_table_size = ARRAY_SIZE(vs_vars);
+	bool unpriv = net->user_ns != &init_user_ns;
 
 	atomic_set(&ipvs->dropentry, 0);
 	spin_lock_init(&ipvs->dropentry_lock);
@@ -4286,12 +4287,6 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
 		tbl = kmemdup(vs_vars, sizeof(vs_vars), GFP_KERNEL);
 		if (tbl == NULL)
 			return -ENOMEM;
-
-		/* Don't export sysctls to unprivileged users */
-		if (net->user_ns != &init_user_ns) {
-			tbl[0].procname = NULL;
-			ctl_table_size = 0;
-		}
 	} else
 		tbl = vs_vars;
 	/* Initialize sysctl defaults */
@@ -4317,10 +4312,17 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
 	ipvs->sysctl_sync_ports = 1;
 	tbl[idx++].data = &ipvs->sysctl_sync_ports;
 	tbl[idx++].data = &ipvs->sysctl_sync_persist_mode;
+
 	ipvs->sysctl_sync_qlen_max = nr_free_buffer_pages() / 32;
+	if (unpriv)
+		tbl[idx].mode = 0444;
 	tbl[idx++].data = &ipvs->sysctl_sync_qlen_max;
+
 	ipvs->sysctl_sync_sock_size = 0;
+	if (unpriv)
+		tbl[idx].mode = 0444;
 	tbl[idx++].data = &ipvs->sysctl_sync_sock_size;
+
 	tbl[idx++].data = &ipvs->sysctl_cache_bypass;
 	tbl[idx++].data = &ipvs->sysctl_expire_nodest_conn;
 	tbl[idx++].data = &ipvs->sysctl_sloppy_tcp;
@@ -4343,15 +4345,22 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
 	tbl[idx++].data = &ipvs->sysctl_conn_reuse_mode;
 	tbl[idx++].data = &ipvs->sysctl_schedule_icmp;
 	tbl[idx++].data = &ipvs->sysctl_ignore_tunneled;
+
 	ipvs->sysctl_run_estimation = 1;
+	if (unpriv)
+		tbl[idx].mode = 0444;
 	tbl[idx].extra2 = ipvs;
 	tbl[idx++].data = &ipvs->sysctl_run_estimation;
 
 	ipvs->est_cpulist_valid = 0;
+	if (unpriv)
+		tbl[idx].mode = 0444;
 	tbl[idx].extra2 = ipvs;
 	tbl[idx++].data = &ipvs->sysctl_est_cpulist;
 
 	ipvs->sysctl_est_nice = IPVS_EST_NICE;
+	if (unpriv)
+		tbl[idx].mode = 0444;
 	tbl[idx].extra2 = ipvs;
 	tbl[idx++].data = &ipvs->sysctl_est_nice;
 
-- 
2.34.1

Re: [PATCH net-next v2 1/2] ipvs: add READ_ONCE barrier for ipvs->sysctl_amemthresh

[Julian Anastasov]

	Hello,

On Thu, 18 Apr 2024, Alexander Mikhalitsyn wrote:

> Cc: Julian Anastasov <ja@ssi.bg>
> Cc: Simon Horman <horms@verge.net.au>
> Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
> Cc: Florian Westphal <fw@strlen.de>
> Suggested-by: Julian Anastasov <ja@ssi.bg>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
> ---
>  net/netfilter/ipvs/ip_vs_ctl.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 143a341bbc0a..daa62b8b2dd1 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c

> @@ -105,7 +106,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
>  	/* si_swapinfo(&i); */
>  	/* availmem = availmem - (i.totalswap - i.freeswap); */
>  
> -	nomem = (availmem < ipvs->sysctl_amemthresh);
> +	amemthresh = max(READ_ONCE(ipvs->sysctl_amemthresh), 0);
> +	nomem = (availmem < amemthresh);
>  
>  	local_bh_disable();
>  
> @@ -146,8 +148,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
>  	case 1:
>  		if (nomem) {
>  			ipvs->drop_rate = ipvs->drop_counter
> -				= ipvs->sysctl_amemthresh /
> -				(ipvs->sysctl_amemthresh-availmem);
> +				= amemthresh /
> +				(amemthresh-availmem);

	Thanks, both patches look ok except that the old styling
is showing warnings for this patch:

scripts/checkpatch.pl --strict /tmp/file1.patch

	It would be great if you silence them somehow in v3...

	BTW, est_cpulist is masked with current->cpus_mask of the
sysctl writer process, if that is of any help. That is why I skipped
it but lets keep it read-only for now...

>  			ipvs->sysctl_drop_packet = 2;
>  		} else {
>  			ipvs->drop_rate = 0;
> @@ -156,8 +158,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
>  	case 2:
>  		if (nomem) {
>  			ipvs->drop_rate = ipvs->drop_counter
> -				= ipvs->sysctl_amemthresh /
> -				(ipvs->sysctl_amemthresh-availmem);
> +				= amemthresh /
> +				(amemthresh-availmem);
>  		} else {
>  			ipvs->drop_rate = 0;
>  			ipvs->sysctl_drop_packet = 1;

Regards

--
Julian Anastasov <ja@ssi.bg>

Re: [PATCH net-next v2 1/2] ipvs: add READ_ONCE barrier for ipvs->sysctl_amemthresh

[Aleksandr Mikhalitsyn]

On Thu, Apr 18, 2024 at 3:23 PM Julian Anastasov <ja@ssi.bg> wrote:
>
>
>         Hello,

Dear Julian,

>
> On Thu, 18 Apr 2024, Alexander Mikhalitsyn wrote:
>
> > Cc: Julian Anastasov <ja@ssi.bg>
> > Cc: Simon Horman <horms@verge.net.au>
> > Cc: Pablo Neira Ayuso <pablo@netfilter.org>
> > Cc: Jozsef Kadlecsik <kadlec@netfilter.org>
> > Cc: Florian Westphal <fw@strlen.de>
> > Suggested-by: Julian Anastasov <ja@ssi.bg>
> > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
> > ---
> >  net/netfilter/ipvs/ip_vs_ctl.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> > index 143a341bbc0a..daa62b8b2dd1 100644
> > --- a/net/netfilter/ipvs/ip_vs_ctl.c
> > +++ b/net/netfilter/ipvs/ip_vs_ctl.c
>
> > @@ -105,7 +106,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
> >       /* si_swapinfo(&i); */
> >       /* availmem = availmem - (i.totalswap - i.freeswap); */
> >
> > -     nomem = (availmem < ipvs->sysctl_amemthresh);
> > +     amemthresh = max(READ_ONCE(ipvs->sysctl_amemthresh), 0);
> > +     nomem = (availmem < amemthresh);
> >
> >       local_bh_disable();
> >
> > @@ -146,8 +148,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
> >       case 1:
> >               if (nomem) {
> >                       ipvs->drop_rate = ipvs->drop_counter
> > -                             = ipvs->sysctl_amemthresh /
> > -                             (ipvs->sysctl_amemthresh-availmem);
> > +                             = amemthresh /
> > +                             (amemthresh-availmem);
>
>         Thanks, both patches look ok except that the old styling
> is showing warnings for this patch:
>
> scripts/checkpatch.pl --strict /tmp/file1.patch
>
>         It would be great if you silence them somehow in v3...

Yeah, I have fixed this in v3. Also, I had to split multiple
assignments into different
lines because of:
>CHECK: multiple assignments should be avoided

Now everything looks fine.

>
>         BTW, est_cpulist is masked with current->cpus_mask of the
> sysctl writer process, if that is of any help. That is why I skipped
> it but lets keep it read-only for now...

That's a good point! Probably I'm too conservative ;-)

>
> >                       ipvs->sysctl_drop_packet = 2;
> >               } else {
> >                       ipvs->drop_rate = 0;
> > @@ -156,8 +158,8 @@ static void update_defense_level(struct netns_ipvs *ipvs)
> >       case 2:
> >               if (nomem) {
> >                       ipvs->drop_rate = ipvs->drop_counter
> > -                             = ipvs->sysctl_amemthresh /
> > -                             (ipvs->sysctl_amemthresh-availmem);
> > +                             = amemthresh /
> > +                             (amemthresh-availmem);
> >               } else {
> >                       ipvs->drop_rate = 0;
> >                       ipvs->sysctl_drop_packet = 1;
>
> Regards

Kind regards,
Alex

>
> --
> Julian Anastasov <ja@ssi.bg>
>