diff options
Diffstat (limited to 'net/sysctl_net.c')
| -rw-r--r-- | net/sysctl_net.c | 65 |
1 files changed, 58 insertions, 7 deletions
diff --git a/net/sysctl_net.c b/net/sysctl_net.c index 9aed6fe1bf1a..19e8048241ba 100644 --- a/net/sysctl_net.c +++ b/net/sysctl_net.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0-only /* -*- linux-c -*- * sysctl_net.c: sysctl interface to net subsystem. * @@ -39,7 +40,7 @@ static int is_seen(struct ctl_table_set *set) /* Return standard mode bits for table entry. */ static int net_ctl_permissions(struct ctl_table_header *head, - struct ctl_table *table) + const struct ctl_table *table) { struct net *net = container_of(head->set, struct net, sysctls); @@ -53,7 +54,6 @@ static int net_ctl_permissions(struct ctl_table_header *head, } 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); @@ -100,7 +100,7 @@ __init int net_sysctl_init(void) * registering "/proc/sys/net" as an empty directory not in a * network namespace. */ - net_header = register_sysctl("net", empty); + net_header = register_sysctl_sz("net", empty, 0); if (!net_header) goto out; ret = register_pernet_subsys(&sysctl_pernet_ops); @@ -114,12 +114,63 @@ out1: goto out; } -struct ctl_table_header *register_net_sysctl(struct net *net, - const char *path, struct ctl_table *table) +/* 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++, 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) { - return __register_sysctl_table(&net->sysctls, path, table); + if (!net_eq(net, &init_net)) + ensure_safe_net_sysctl(net, path, table, table_size); + + return __register_sysctl_table(&net->sysctls, path, table, table_size); } -EXPORT_SYMBOL_GPL(register_net_sysctl); +EXPORT_SYMBOL_GPL(register_net_sysctl_sz); void unregister_net_sysctl_table(struct ctl_table_header *header) { |