diff options
Diffstat (limited to 'net/sysctl_net.c')
| -rw-r--r-- | net/sysctl_net.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/net/sysctl_net.c b/net/sysctl_net.c index d14dab8b6774..f6cb0d4d114c 100644 --- a/net/sysctl_net.c +++ b/net/sysctl_net.c @@ -115,9 +115,57 @@ out1: 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) +{ + struct ctl_table *ent; + + pr_debug("Registering net sysctl (net %p): %s\n", net, path); + for (ent = table; ent->procname; ent++) { + 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 (core_kernel_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(struct net *net, const char *path, struct ctl_table *table) { + if (!net_eq(net, &init_net)) + ensure_safe_net_sysctl(net, path, table); + return __register_sysctl_table(&net->sysctls, path, table); } EXPORT_SYMBOL_GPL(register_net_sysctl); |