Re: [PATCH 06/11] sysctl: Add size to register_net_sysctl function

From: Joel Granados
Date: Wed Jun 21 2023 - 08:04:01 EST

Hey Dan

On Wed, Jun 21, 2023 at 01:23:52PM +0300, Dan Carpenter wrote:
> On Wed, Jun 21, 2023 at 12:47:30PM +0300, Dan Carpenter wrote:
> > The patchset doesn't include the actual interesting changes, just a
> > bunch of mechanical prep work.
> >
> > On Wed, Jun 21, 2023 at 11:09:55AM +0200, Joel Granados wrote:
> > > diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c
> > > index a91283d1e5bf..7b717434368c 100644
> > > --- a/net/ieee802154/6lowpan/reassembly.c
> > > +++ b/net/ieee802154/6lowpan/reassembly.c
> > > @@ -379,7 +379,8 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
> > > table[1].extra2 = &ieee802154_lowpan->fqdir->high_thresh;
> > > table[2].data = &ieee802154_lowpan->fqdir->timeout;
> > >
> > > - hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
> > > + hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table,
> > > + ARRAY_SIZE(lowpan_frags_ns_ctl_table));
> >
> > For example, in lowpan_frags_ns_sysctl_register() the sentinel is
> > sometimes element zero if the user doesn't have enough permissions. I
> > would want to ensure that was handled correctly, but that's going to be
> > done later in a completely different patchset. I'm definitely not going
> > to remember to check.
>
> On reflecting the patch is obviously wrong. It should be pass zero as
> table_size in that case. See diff at the end.
yes

>
> There is a similar bug in neigh_sysctl_register() where we use memset to
> zero out the whole table. And another in __ip_vs_lblc_init(). I used
> the smatch cross function database
> `smdb.py where ctl_table procname | grep '(null)' | grep min-max`
> to make a list of functions which set procname to zero.
Awesome. That is homework on my part for V2. It gives me a way forward.
Thx!!!

>
> Probably we should add a WARN_ON() if procname is zero in the new code
> which doesn't use sentinels.
Yes

>
> regards,
> dan carpenter
>
> drivers/char/random.c | proc_do_uuid | (struct ctl_table)->procname | 0
> fs/proc/proc_sysctl.c | new_dir | (struct ctl_table)->procname | 48,3906148897379000352
> fs/proc/proc_sysctl.c | new_links | (struct ctl_table)->procname | 4096-ptr_max
> arch/arm64/kernel/fpsimd.c | vec_proc_do_default_vl | (struct ctl_table)->procname | 0
> arch/arm64/kernel/armv8_deprecated.c | register_insn_emulation | (struct ctl_table)->procname | 0-u64max
> kernel/sysctl-test.c | sysctl_test_api_dointvec_null_tbl_data | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_api_dointvec_table_maxlen_unset | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_api_dointvec_table_len_is_zero | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_api_dointvec_table_read_but_position_set | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_dointvec_read_happy_single_positive | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_dointvec_read_happy_single_negative | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_dointvec_write_happy_single_positive | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_dointvec_write_happy_single_negative | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_api_dointvec_write_single_less_int_min | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl-test.c | sysctl_test_api_dointvec_write_single_greater_int_max | (struct ctl_table)->procname | 7612622206476333056
> kernel/sysctl.c | proc_do_static_key | (struct ctl_table)->procname | 0
> kernel/kexec_core.c | kexec_limit_handler | (struct ctl_table)->procname | 0
> kernel/bpf/syscall.c | bpf_stats_handler | (struct ctl_table)->procname | 0
> net/core/sysctl_net_core.c | rps_sock_flow_sysctl | (struct ctl_table)->procname | 0
> net/core/sysctl_net_core.c | set_default_qdisc | (struct ctl_table)->procname | 0
> net/core/neighbour.c | neigh_sysctl_register | (struct ctl_table)->procname | 0
> net/netfilter/ipvs/ip_vs_lblc.c | __ip_vs_lblc_init | (struct ctl_table)->procname | 0-u64max
> net/netfilter/ipvs/ip_vs_lblcr.c | __ip_vs_lblcr_init | (struct ctl_table)->procname | 0-u64max
> net/netfilter/ipvs/ip_vs_ctl.c | proc_do_defense_mode | (struct ctl_table)->procname | 0
> net/netfilter/ipvs/ip_vs_ctl.c | proc_do_sync_threshold | (struct ctl_table)->procname | 0
> net/netfilter/ipvs/ip_vs_ctl.c | proc_do_sync_ports | (struct ctl_table)->procname | 0
> net/netfilter/ipvs/ip_vs_ctl.c | ipvs_proc_est_nice | (struct ctl_table)->procname | 0
> net/netfilter/ipvs/ip_vs_ctl.c | ipvs_proc_run_estimation | (struct ctl_table)->procname | 0
> net/netfilter/ipvs/ip_vs_ctl.c | ip_vs_control_net_init_sysctl | (struct ctl_table)->procname | 0-u64max
> net/netfilter/nf_log.c | netfilter_log_sysctl_init | (struct ctl_table)->procname | 0-u64max
> net/sctp/sysctl.c | proc_sctp_do_hmac_alg | (struct ctl_table)->procname | 0
> net/sctp/sysctl.c | proc_sctp_do_rto_min | (struct ctl_table)->procname | 0
> net/sctp/sysctl.c | proc_sctp_do_rto_max | (struct ctl_table)->procname | 0
> net/sctp/sysctl.c | proc_sctp_do_auth | (struct ctl_table)->procname | 0
> net/sctp/sysctl.c | proc_sctp_do_udp_port | (struct ctl_table)->procname | 0
> net/sctp/sysctl.c | proc_sctp_do_probe_interval | (struct ctl_table)->procname | 0
> net/ipv6/route.c | ipv6_route_sysctl_init | (struct ctl_table)->procname | 0-u64max
> net/ipv6/addrconf.c | addrconf_sysctl_addr_gen_mode | (struct ctl_table)->procname | 0
> net/ieee802154/6lowpan/reassembly.c | lowpan_frags_ns_sysctl_register | (struct ctl_table)->procname | 0-u64max
> net/xfrm/xfrm_sysctl.c | xfrm_sysctl_init | (struct ctl_table)->procname | 0-u64max
> net/phonet/sysctl.c | proc_local_port_range | (struct ctl_table)->procname | 0
> net/ipv4/route.c | sysctl_route_net_init | (struct ctl_table)->procname | 0-u64max
> net/ipv4/sysctl_net_ipv4.c | ipv4_local_port_range | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | ipv4_privileged_ports | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | ipv4_ping_group_range | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | proc_tcp_congestion_control | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | proc_tcp_available_congestion_control | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | proc_allowed_congestion_control | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | proc_tcp_fastopen_key | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | proc_tcp_available_ulp | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | proc_tcp_ehash_entries | (struct ctl_table)->procname | 0
> net/ipv4/sysctl_net_ipv4.c | proc_udp_hash_entries | (struct ctl_table)->procname | 0
>
> diff --git a/net/ieee802154/6lowpan/reassembly.c b/net/ieee802154/6lowpan/reassembly.c
> index a91283d1e5bf..749238d38014 100644
> --- a/net/ieee802154/6lowpan/reassembly.c
> +++ b/net/ieee802154/6lowpan/reassembly.c
> @@ -360,6 +360,7 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
> struct ctl_table_header *hdr;
> struct netns_ieee802154_lowpan *ieee802154_lowpan =
> net_ieee802154_lowpan(net);
> + size_t table_size = ARRAY_SIZE(lowpan_frags_ns_ctl_table);
>
> table = lowpan_frags_ns_ctl_table;
> if (!net_eq(net, &init_net)) {
> @@ -369,8 +370,10 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
> goto err_alloc;
>
> /* Don't export sysctls to unprivileged users */
> - if (net->user_ns != &init_user_ns)
> + if (net->user_ns != &init_user_ns) {
> table[0].procname = NULL;
> + table_size = 0;
> + }
> }
>
> table[0].data = &ieee802154_lowpan->fqdir->high_thresh;
> @@ -379,7 +382,7 @@ static int __net_init lowpan_frags_ns_sysctl_register(struct net *net)
> table[1].extra2 = &ieee802154_lowpan->fqdir->high_thresh;
> table[2].data = &ieee802154_lowpan->fqdir->timeout;
>
> - hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table);
> + hdr = register_net_sysctl(net, "net/ieee802154/6lowpan", table, table_size);
> if (hdr == NULL)
> goto err_reg;
>

--

Joel Granados

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