diff options
Diffstat (limited to 'net/sysctl_net.c')
| -rw-r--r-- | net/sysctl_net.c | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/net/sysctl_net.c b/net/sysctl_net.c new file mode 100644 index 000000000..051ed5f6f --- /dev/null +++ b/net/sysctl_net.c @@ -0,0 +1,187 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* -*- linux-c -*- + * sysctl_net.c: sysctl interface to net subsystem. + * + * Begun April 1, 1996, Mike Shaver. + * Added /proc/sys/net directories for each protocol family. [MS] + * + * Revision 1.2 1996/05/08 20:24:40 shaver + * Added bits for NET_BRIDGE and the NET_IPV4_ARP stuff and + * NET_IPV4_IP_FORWARD. + * + * + */ + +#include <linux/mm.h> +#include <linux/export.h> +#include <linux/sysctl.h> +#include <linux/nsproxy.h> + +#include <net/sock.h> + +#ifdef CONFIG_INET +#include <net/ip.h> +#endif + +#ifdef CONFIG_NET +#include <linux/if_ether.h> +#endif + +static struct ctl_table_set * +net_ctl_header_lookup(struct ctl_table_root *root) +{ + return ¤t->nsproxy->net_ns->sysctls; +} + +static int is_seen(struct ctl_table_set *set) +{ + return ¤t->nsproxy->net_ns->sysctls == set; +} + +/* Return standard mode bits for table entry. */ +static int net_ctl_permissions(struct ctl_table_header *head, + struct ctl_table *table) +{ + struct net *net = container_of(head->set, struct net, sysctls); + + /* Allow network administrator to have same access as root. */ + if (ns_capable_noaudit(net->user_ns, CAP_NET_ADMIN)) { + int mode = (table->mode >> 6) & 7; + return (mode << 6) | (mode << 3) | mode; + } + + return table->mode; +} + +static void net_ctl_set_ownership(struct ctl_table_header *head, + struct ctl_table *table, + kuid_t *uid, kgid_t *gid) +{ + struct net *net = container_of(head->set, struct net, sysctls); + kuid_t ns_root_uid; + kgid_t ns_root_gid; + + ns_root_uid = make_kuid(net->user_ns, 0); + if (uid_valid(ns_root_uid)) + *uid = ns_root_uid; + + ns_root_gid = make_kgid(net->user_ns, 0); + if (gid_valid(ns_root_gid)) + *gid = ns_root_gid; +} + +static struct ctl_table_root net_sysctl_root = { + .lookup = net_ctl_header_lookup, + .permissions = net_ctl_permissions, + .set_ownership = net_ctl_set_ownership, +}; + +static int __net_init sysctl_net_init(struct net *net) +{ + setup_sysctl_set(&net->sysctls, &net_sysctl_root, is_seen); + return 0; +} + +static void __net_exit sysctl_net_exit(struct net *net) +{ + retire_sysctl_set(&net->sysctls); +} + +static struct pernet_operations sysctl_pernet_ops = { + .init = sysctl_net_init, + .exit = sysctl_net_exit, +}; + +static struct ctl_table_header *net_header; +__init int net_sysctl_init(void) +{ + static struct ctl_table empty[1]; + int ret = -ENOMEM; + /* Avoid limitations in the sysctl implementation by + * registering "/proc/sys/net" as an empty directory not in a + * network namespace. + */ + net_header = register_sysctl_sz("net", empty, 0); + if (!net_header) + goto out; + ret = register_pernet_subsys(&sysctl_pernet_ops); + if (ret) + goto out1; +out: + return ret; +out1: + unregister_sysctl_table(net_header); + net_header = NULL; + goto out; +} + +/* Verify that sysctls for non-init netns are safe by either: + * 1) being read-only, or + * 2) having a data pointer which points outside of the global kernel/module + * data segment, and rather into the heap where a per-net object was + * allocated. + */ +static void ensure_safe_net_sysctl(struct net *net, const char *path, + struct ctl_table *table, size_t table_size) +{ + struct ctl_table *ent; + + pr_debug("Registering net sysctl (net %p): %s\n", net, path); + ent = table; + for (size_t i = 0; i < table_size && ent->procname; ent++, i++) { + unsigned long addr; + const char *where; + + pr_debug(" procname=%s mode=%o proc_handler=%ps data=%p\n", + ent->procname, ent->mode, ent->proc_handler, ent->data); + + /* If it's not writable inside the netns, then it can't hurt. */ + if ((ent->mode & 0222) == 0) { + pr_debug(" Not writable by anyone\n"); + continue; + } + + /* Where does data point? */ + addr = (unsigned long)ent->data; + if (is_module_address(addr)) + where = "module"; + else if (is_kernel_core_data(addr)) + where = "kernel"; + else + continue; + + /* If it is writable and points to kernel/module global + * data, then it's probably a netns leak. + */ + WARN(1, "sysctl %s/%s: data points to %s global data: %ps\n", + path, ent->procname, where, ent->data); + + /* Make it "safe" by dropping writable perms */ + ent->mode &= ~0222; + } +} + +struct ctl_table_header *register_net_sysctl_sz(struct net *net, + const char *path, + struct ctl_table *table, + size_t table_size) +{ + int count; + struct ctl_table *entry; + + if (!net_eq(net, &init_net)) + ensure_safe_net_sysctl(net, path, table, table_size); + + entry = table; + for (count = 0 ; count < table_size && entry->procname; entry++, count++) + ; + + return __register_sysctl_table(&net->sysctls, path, table, count); +} +EXPORT_SYMBOL_GPL(register_net_sysctl_sz); + +void unregister_net_sysctl_table(struct ctl_table_header *header) +{ + unregister_sysctl_table(header); +} +EXPORT_SYMBOL_GPL(unregister_net_sysctl_table); |