diff options
Diffstat (limited to 'fs/cifs/dns_resolve.c')
| -rw-r--r-- | fs/cifs/dns_resolve.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c index 87948147d7ec..31da21f0654c 100644 --- a/fs/cifs/dns_resolve.c +++ b/fs/cifs/dns_resolve.c @@ -23,12 +23,16 @@ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ +#include <linux/keyctl.h> +#include <linux/key-type.h> #include <keys/user-type.h> #include "dns_resolve.h" #include "cifsglob.h" #include "cifsproto.h" #include "cifs_debug.h" +static const struct cred *dns_resolver_cache; + /* Checks if supplied name is IP address * returns: * 1 - name is IP @@ -93,6 +97,7 @@ struct key_type key_type_dns_resolver = { int dns_resolve_server_name_to_ip(const char *unc, char **ip_addr) { + const struct cred *saved_cred; int rc = -EAGAIN; struct key *rkey = ERR_PTR(-EAGAIN); char *name; @@ -132,8 +137,15 @@ dns_resolve_server_name_to_ip(const char *unc, char **ip_addr) goto skip_upcall; } + saved_cred = override_creds(dns_resolver_cache); rkey = request_key(&key_type_dns_resolver, name, ""); + revert_creds(saved_cred); if (!IS_ERR(rkey)) { + if (!(rkey->perm & KEY_USR_VIEW)) { + down_read(&rkey->sem); + rkey->perm |= KEY_USR_VIEW; + up_read(&rkey->sem); + } len = rkey->type_data.x[0]; data = rkey->payload.data; } else { @@ -164,4 +176,61 @@ out: return rc; } +int __init cifs_init_dns_resolver(void) +{ + struct cred *cred; + struct key *keyring; + int ret; + + printk(KERN_NOTICE "Registering the %s key type\n", + key_type_dns_resolver.name); + + /* create an override credential set with a special thread keyring in + * which DNS requests are cached + * + * this is used to prevent malicious redirections from being installed + * with add_key(). + */ + cred = prepare_kernel_cred(NULL); + if (!cred) + return -ENOMEM; + + keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred, + (KEY_POS_ALL & ~KEY_POS_SETATTR) | + KEY_USR_VIEW | KEY_USR_READ, + KEY_ALLOC_NOT_IN_QUOTA); + if (IS_ERR(keyring)) { + ret = PTR_ERR(keyring); + goto failed_put_cred; + } + + ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL); + if (ret < 0) + goto failed_put_key; + + ret = register_key_type(&key_type_dns_resolver); + if (ret < 0) + goto failed_put_key; + + /* instruct request_key() to use this special keyring as a cache for + * the results it looks up */ + cred->thread_keyring = keyring; + cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; + dns_resolver_cache = cred; + return 0; + +failed_put_key: + key_put(keyring); +failed_put_cred: + put_cred(cred); + return ret; +} +void cifs_exit_dns_resolver(void) +{ + key_revoke(dns_resolver_cache->thread_keyring); + unregister_key_type(&key_type_dns_resolver); + put_cred(dns_resolver_cache); + printk(KERN_NOTICE "Unregistered %s key type\n", + key_type_dns_resolver.name); +} |