| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* -*- linux-c -*- |
| 3 | * sysctl_net.c: sysctl interface to net subsystem. |
| 4 | * |
| 5 | * Begun April 1, 1996, Mike Shaver. |
| 6 | * Added /proc/sys/net directories for each protocol family. [MS] |
| 7 | * |
| 8 | * Revision 1.2 1996/05/08 20:24:40 shaver |
| 9 | * Added bits for NET_BRIDGE and the NET_IPV4_ARP stuff and |
| 10 | * NET_IPV4_IP_FORWARD. |
| 11 | * |
| 12 | * |
| 13 | */ |
| 14 | |
| 15 | #include <linux/mm.h> |
| 16 | #include <linux/export.h> |
| 17 | #include <linux/sysctl.h> |
| 18 | #include <linux/nsproxy.h> |
| 19 | |
| 20 | #include <net/sock.h> |
| 21 | |
| 22 | #ifdef CONFIG_INET |
| 23 | #include <net/ip.h> |
| 24 | #endif |
| 25 | |
| 26 | #ifdef CONFIG_NET |
| 27 | #include <linux/if_ether.h> |
| 28 | #endif |
| 29 | |
| 30 | static struct ctl_table_set * |
| 31 | net_ctl_header_lookup(struct ctl_table_root *root) |
| 32 | { |
| 33 | return ¤t->nsproxy->net_ns->sysctls; |
| 34 | } |
| 35 | |
| 36 | static int is_seen(struct ctl_table_set *set) |
| 37 | { |
| 38 | return ¤t->nsproxy->net_ns->sysctls == set; |
| 39 | } |
| 40 | |
| 41 | /* Return standard mode bits for table entry. */ |
| 42 | static int net_ctl_permissions(struct ctl_table_header *head, |
| 43 | struct ctl_table *table) |
| 44 | { |
| 45 | struct net *net = container_of(head->set, struct net, sysctls); |
| 46 | |
| 47 | /* Allow network administrator to have same access as root. */ |
| 48 | if (ns_capable_noaudit(net->user_ns, CAP_NET_ADMIN)) { |
| 49 | int mode = (table->mode >> 6) & 7; |
| 50 | return (mode << 6) | (mode << 3) | mode; |
| 51 | } |
| 52 | |
| 53 | return table->mode; |
| 54 | } |
| 55 | |
| 56 | static void net_ctl_set_ownership(struct ctl_table_header *head, |
| 57 | struct ctl_table *table, |
| 58 | kuid_t *uid, kgid_t *gid) |
| 59 | { |
| 60 | struct net *net = container_of(head->set, struct net, sysctls); |
| 61 | kuid_t ns_root_uid; |
| 62 | kgid_t ns_root_gid; |
| 63 | |
| 64 | ns_root_uid = make_kuid(net->user_ns, 0); |
| 65 | if (uid_valid(ns_root_uid)) |
| 66 | *uid = ns_root_uid; |
| 67 | |
| 68 | ns_root_gid = make_kgid(net->user_ns, 0); |
| 69 | if (gid_valid(ns_root_gid)) |
| 70 | *gid = ns_root_gid; |
| 71 | } |
| 72 | |
| 73 | static struct ctl_table_root net_sysctl_root = { |
| 74 | .lookup = net_ctl_header_lookup, |
| 75 | .permissions = net_ctl_permissions, |
| 76 | .set_ownership = net_ctl_set_ownership, |
| 77 | }; |
| 78 | |
| 79 | static int __net_init sysctl_net_init(struct net *net) |
| 80 | { |
| 81 | setup_sysctl_set(&net->sysctls, &net_sysctl_root, is_seen); |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | static void __net_exit sysctl_net_exit(struct net *net) |
| 86 | { |
| 87 | retire_sysctl_set(&net->sysctls); |
| 88 | } |
| 89 | |
| 90 | static struct pernet_operations sysctl_pernet_ops = { |
| 91 | .init = sysctl_net_init, |
| 92 | .exit = sysctl_net_exit, |
| 93 | }; |
| 94 | |
| 95 | static struct ctl_table_header *net_header; |
| 96 | __init int net_sysctl_init(void) |
| 97 | { |
| 98 | static struct ctl_table empty[1]; |
| 99 | int ret = -ENOMEM; |
| 100 | /* Avoid limitations in the sysctl implementation by |
| 101 | * registering "/proc/sys/net" as an empty directory not in a |
| 102 | * network namespace. |
| 103 | */ |
| 104 | net_header = register_sysctl_sz("net", empty, 0); |
| 105 | if (!net_header) |
| 106 | goto out; |
| 107 | ret = register_pernet_subsys(&sysctl_pernet_ops); |
| 108 | if (ret) |
| 109 | goto out1; |
| 110 | out: |
| 111 | return ret; |
| 112 | out1: |
| 113 | unregister_sysctl_table(net_header); |
| 114 | net_header = NULL; |
| 115 | goto out; |
| 116 | } |
| 117 | |
| 118 | /* Verify that sysctls for non-init netns are safe by either: |
| 119 | * 1) being read-only, or |
| 120 | * 2) having a data pointer which points outside of the global kernel/module |
| 121 | * data segment, and rather into the heap where a per-net object was |
| 122 | * allocated. |
| 123 | */ |
| 124 | static void ensure_safe_net_sysctl(struct net *net, const char *path, |
| 125 | struct ctl_table *table, size_t table_size) |
| 126 | { |
| 127 | struct ctl_table *ent; |
| 128 | |
| 129 | pr_debug("Registering net sysctl (net %p): %s\n", net, path); |
| 130 | ent = table; |
| 131 | for (size_t i = 0; i < table_size && ent->procname; ent++, i++) { |
| 132 | unsigned long addr; |
| 133 | const char *where; |
| 134 | |
| 135 | pr_debug(" procname=%s mode=%o proc_handler=%ps data=%p\n", |
| 136 | ent->procname, ent->mode, ent->proc_handler, ent->data); |
| 137 | |
| 138 | /* If it's not writable inside the netns, then it can't hurt. */ |
| 139 | if ((ent->mode & 0222) == 0) { |
| 140 | pr_debug(" Not writable by anyone\n"); |
| 141 | continue; |
| 142 | } |
| 143 | |
| 144 | /* Where does data point? */ |
| 145 | addr = (unsigned long)ent->data; |
| 146 | if (is_module_address(addr)) |
| 147 | where = "module"; |
| 148 | else if (is_kernel_core_data(addr)) |
| 149 | where = "kernel"; |
| 150 | else |
| 151 | continue; |
| 152 | |
| 153 | /* If it is writable and points to kernel/module global |
| 154 | * data, then it's probably a netns leak. |
| 155 | */ |
| 156 | WARN(1, "sysctl %s/%s: data points to %s global data: %ps\n", |
| 157 | path, ent->procname, where, ent->data); |
| 158 | |
| 159 | /* Make it "safe" by dropping writable perms */ |
| 160 | ent->mode &= ~0222; |
| 161 | } |
| 162 | } |
| 163 | |
| 164 | struct ctl_table_header *register_net_sysctl_sz(struct net *net, |
| 165 | const char *path, |
| 166 | struct ctl_table *table, |
| 167 | size_t table_size) |
| 168 | { |
| 169 | int count; |
| 170 | struct ctl_table *entry; |
| 171 | |
| 172 | if (!net_eq(net, &init_net)) |
| 173 | ensure_safe_net_sysctl(net, path, table, table_size); |
| 174 | |
| 175 | entry = table; |
| 176 | for (count = 0 ; count < table_size && entry->procname; entry++, count++) |
| 177 | ; |
| 178 | |
| 179 | return __register_sysctl_table(&net->sysctls, path, table, count); |
| 180 | } |
| 181 | EXPORT_SYMBOL_GPL(register_net_sysctl_sz); |
| 182 | |
| 183 | void unregister_net_sysctl_table(struct ctl_table_header *header) |
| 184 | { |
| 185 | unregister_sysctl_table(header); |
| 186 | } |
| 187 | EXPORT_SYMBOL_GPL(unregister_net_sysctl_table); |