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

From: Dan Carpenter
Date: Wed Jun 21 2023 - 06:24:23 EST

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.

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.

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

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;