diff options
| -rw-r--r-- | fs/cifs/cifsfs.c | 6 | ||||
| -rw-r--r-- | fs/cifs/dns_resolve.c | 69 | ||||
| -rw-r--r-- | fs/cifs/dns_resolve.h | 4 |
3 files changed, 74 insertions, 5 deletions
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 484e52bb40b..2cb1a70214d 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -923,7 +923,7 @@ init_cifs(void) goto out_unregister_filesystem; #endif #ifdef CONFIG_CIFS_DFS_UPCALL - rc = register_key_type(&key_type_dns_resolver); + rc = cifs_init_dns_resolver(); if (rc) goto out_unregister_key_type; #endif @@ -935,7 +935,7 @@ init_cifs(void) out_unregister_resolver_key: #ifdef CONFIG_CIFS_DFS_UPCALL - unregister_key_type(&key_type_dns_resolver); + cifs_exit_dns_resolver(); out_unregister_key_type: #endif #ifdef CONFIG_CIFS_UPCALL @@ -961,7 +961,7 @@ exit_cifs(void) cifs_proc_clean(); #ifdef CONFIG_CIFS_DFS_UPCALL cifs_dfs_release_automount_timer(); - unregister_key_type(&key_type_dns_resolver); + cifs_exit_dns_resolver(); #endif #ifdef CONFIG_CIFS_UPCALL unregister_key_type(&cifs_spnego_key_type); diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c index 4db2c5e7283..49315cbf742 100644 --- a/fs/cifs/dns_resolve.c +++ b/fs/cifs/dns_resolve.c @@ -24,12 +24,16 @@ */ #include <linux/slab.h> +#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 @@ -94,6 +98,7 @@ 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; @@ -133,8 +138,15 @@ 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 { @@ -165,4 +177,61 @@ 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 __exit 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); +} diff --git a/fs/cifs/dns_resolve.h b/fs/cifs/dns_resolve.h index 966e9288930..26b9eaa9f5e 100644 --- a/fs/cifs/dns_resolve.h +++ b/fs/cifs/dns_resolve.h @@ -24,8 +24,8 @@ #define _DNS_RESOLVE_H #ifdef __KERNEL__ -#include <linux/key-type.h> -extern struct key_type key_type_dns_resolver; +extern int __init cifs_init_dns_resolver(void); +extern void __exit cifs_exit_dns_resolver(void); extern int dns_resolve_server_name_to_ip(const char *unc, char **ip_addr); #endif /* KERNEL */ |