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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 07/11] keys: Move the user and user-session keyrings to the user_namespace From: David Howells To: ebiederm@xmission.com Cc: Jann Horn , keyrings@vger.kernel.org, dhowells@redhat.com, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, dwalsh@redhat.com, vgoyal@redhat.com Date: Wed, 24 Apr 2019 17:14:27 +0100 Message-ID: <155612246750.8564.9186344007442012471.stgit@warthog.procyon.org.uk> In-Reply-To: <155612240208.8564.13865046977065545591.stgit@warthog.procyon.org.uk> References: <155612240208.8564.13865046977065545591.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 24 Apr 2019 16:14:30 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Move the user and user-session keyrings to the user_namespace struct rather than pinning them from the user_struct struct. This prevents these keyrings from propagating across user-namespaces boundaries with regard to the KEY_SPEC_* flags, thereby making them more useful in a containerised environment. The issue is that a single user_struct may be represent UIDs in several different namespaces. The way the patch does this is by attaching a 'register keyring' in each user_namespace and then sticking the user and user-session keyrings into that. It can then be searched to retrieve them. Signed-off-by: David Howells cc: Jann Horn --- include/linux/sched/user.h | 14 -- include/linux/user_namespace.h | 3 kernel/user.c | 9 - kernel/user_namespace.c | 4 - security/keys/internal.h | 3 security/keys/keyring.c | 1 security/keys/persistent.c | 8 + security/keys/process_keys.c | 249 +++++++++++++++++++++++++--------------- security/keys/request_key.c | 21 ++- 9 files changed, 181 insertions(+), 131 deletions(-) diff --git a/include/linux/sched/user.h b/include/linux/sched/user.h index 468d2565a9fe..917d88edb7b9 100644 --- a/include/linux/sched/user.h +++ b/include/linux/sched/user.h @@ -7,8 +7,6 @@ #include #include -struct key; - /* * Some day this will be a full-fledged user tracking system.. */ @@ -30,18 +28,6 @@ struct user_struct { unsigned long unix_inflight; /* How many files in flight in unix sockets */ atomic_long_t pipe_bufs; /* how many pages are allocated in pipe buffers */ -#ifdef CONFIG_KEYS - /* - * These pointers can only change from NULL to a non-NULL value once. - * Writes are protected by key_user_keyring_mutex. - * Unlocked readers should use READ_ONCE() unless they know that - * install_user_keyrings() has been called successfully (which sets - * these members to non-NULL values, preventing further modifications). - */ - struct key *uid_keyring; /* UID specific keyring */ - struct key *session_keyring; /* UID's default session keyring */ -#endif - /* Hash table maintenance information */ struct hlist_node uidhash_node; kuid_t uid; diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index 90457015fa3f..44a5a4a8a269 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -67,12 +67,13 @@ struct user_namespace { #ifdef CONFIG_KEYS /* List of joinable keyrings in this namespace */ struct list_head keyring_name_list; + struct key *user_keyring_register; + struct rw_semaphore keyring_sem; #endif /* Register of per-UID persistent keyrings for this namespace */ #ifdef CONFIG_PERSISTENT_KEYRINGS struct key *persistent_keyring_register; - struct rw_semaphore persistent_keyring_register_sem; #endif struct work_struct work; #ifdef CONFIG_SYSCTL diff --git a/kernel/user.c b/kernel/user.c index 6a6ccb99f31a..63bde2144338 100644 --- a/kernel/user.c +++ b/kernel/user.c @@ -64,10 +64,7 @@ struct user_namespace init_user_ns = { .flags = USERNS_INIT_FLAGS, #ifdef CONFIG_KEYS .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list), -#endif -#ifdef CONFIG_PERSISTENT_KEYRINGS - .persistent_keyring_register_sem = - __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem), + .keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem), #endif }; EXPORT_SYMBOL_GPL(init_user_ns); @@ -143,8 +140,6 @@ static void free_user(struct user_struct *up, unsigned long flags) { uid_hash_remove(up); spin_unlock_irqrestore(&uidhash_lock, flags); - key_put(up->uid_keyring); - key_put(up->session_keyring); kmem_cache_free(uid_cachep, up); } @@ -202,8 +197,6 @@ struct user_struct *alloc_uid(kuid_t uid) spin_lock_irq(&uidhash_lock); up = uid_hash_find(uid, hashent); if (up) { - key_put(new->uid_keyring); - key_put(new->session_keyring); kmem_cache_free(uid_cachep, new); } else { uid_hash_insert(new, hashent); diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index bda6e890ad88..c87c2ecc7085 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -135,9 +135,7 @@ int create_user_ns(struct cred *new) #ifdef CONFIG_KEYS INIT_LIST_HEAD(&ns->keyring_name_list); -#endif -#ifdef CONFIG_PERSISTENT_KEYRINGS - init_rwsem(&ns->persistent_keyring_register_sem); + init_rwsem(&ns->keyring_sem); #endif ret = -ENOMEM; if (!setup_userns_sysctls(ns)) diff --git a/security/keys/internal.h b/security/keys/internal.h index 8ac7573bf23b..ea48d8b30794 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -144,7 +144,8 @@ extern key_ref_t search_process_keyrings(struct keyring_search_context *ctx); extern struct key *find_keyring_by_name(const char *name, bool uid_keyring); -extern int install_user_keyrings(void); +extern int look_up_user_keyrings(struct key **, struct key **); +extern struct key *get_user_session_keyring(void); extern int install_thread_keyring_to_cred(struct cred *); extern int install_process_keyring_to_cred(struct cred *); extern int install_session_keyring_to_cred(struct cred *, struct key *); diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 48eda80afe89..1fc9219ed002 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -62,6 +62,7 @@ void key_free_user_ns(struct user_namespace *ns) list_del_init(&ns->keyring_name_list); write_unlock(&keyring_name_lock); + key_put(ns->user_keyring_register); #ifdef CONFIG_PERSISTENT_KEYRINGS key_put(ns->persistent_keyring_register); #endif diff --git a/security/keys/persistent.c b/security/keys/persistent.c index fc29ec59efa7..90303fe4a394 100644 --- a/security/keys/persistent.c +++ b/security/keys/persistent.c @@ -91,9 +91,9 @@ static long key_get_persistent(struct user_namespace *ns, kuid_t uid, if (ns->persistent_keyring_register) { reg_ref = make_key_ref(ns->persistent_keyring_register, true); - down_read(&ns->persistent_keyring_register_sem); + down_read(&ns->keyring_sem); persistent_ref = find_key_to_update(reg_ref, &index_key); - up_read(&ns->persistent_keyring_register_sem); + up_read(&ns->keyring_sem); if (persistent_ref) goto found; @@ -102,9 +102,9 @@ static long key_get_persistent(struct user_namespace *ns, kuid_t uid, /* It wasn't in the register, so we'll need to create it. We might * also need to create the register. */ - down_write(&ns->persistent_keyring_register_sem); + down_write(&ns->keyring_sem); persistent_ref = key_create_persistent(ns, uid, &index_key); - up_write(&ns->persistent_keyring_register_sem); + up_write(&ns->keyring_sem); if (!IS_ERR(persistent_ref)) goto found; diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c index 70fa20888ca8..ff62d90415ae 100644 --- a/security/keys/process_keys.c +++ b/security/keys/process_keys.c @@ -8,7 +8,7 @@ * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ - +#define __KDEBUG #include #include #include @@ -19,15 +19,13 @@ #include #include #include +#include #include #include "internal.h" /* Session keyring create vs join semaphore */ static DEFINE_MUTEX(key_session_mutex); -/* User keyring creation semaphore */ -static DEFINE_MUTEX(key_user_keyring_mutex); - /* The root user's tracking struct */ struct key_user root_key_user = { .usage = REFCOUNT_INIT(3), @@ -39,98 +37,173 @@ struct key_user root_key_user = { }; /* - * Install the user and user session keyrings for the current process's UID. + * Get or create a user register keyring. */ -int install_user_keyrings(void) +static struct key *get_user_register(struct user_namespace *user_ns) { - struct user_struct *user; - const struct cred *cred; - struct key *uid_keyring, *session_keyring; + struct key *reg_keyring = user_ns->user_keyring_register; + + if (reg_keyring) + return reg_keyring; + + down_write(&user_ns->keyring_sem); + + /* Make sure there's a register keyring. It gets owned by the + * user_namespace's owner. + */ + reg_keyring = user_ns->user_keyring_register; + if (!reg_keyring) { + reg_keyring = keyring_alloc(".user_reg", user_ns->owner, INVALID_GID, + &init_cred, + KEY_POS_WRITE | KEY_POS_SEARCH | + KEY_USR_VIEW | KEY_USR_READ, + 0, + NULL, NULL); + if (!IS_ERR(reg_keyring)) + user_ns->user_keyring_register = reg_keyring; + } + + up_write(&user_ns->keyring_sem); + + /* We don't return a ref since the keyring is pinned by the user_ns */ + return reg_keyring; +} + +/* + * Look up the user and user session keyrings for the current process's UID, + * creating them if they don't exist. + */ +int look_up_user_keyrings(struct key **_user_keyring, + struct key **_user_session_keyring) +{ + const struct cred *cred = current_cred(); + struct user_namespace *user_ns = current_user_ns(); + struct key *reg_keyring, *uid_keyring, *session_keyring; key_perm_t user_keyring_perm; + key_ref_t uid_keyring_r, session_keyring_r; + uid_t uid = from_kuid(user_ns, cred->user->uid); char buf[20]; int ret; - uid_t uid; user_keyring_perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL; - cred = current_cred(); - user = cred->user; - uid = from_kuid(cred->user_ns, user->uid); - kenter("%p{%u}", user, uid); + kenter("%u", uid); - if (READ_ONCE(user->uid_keyring) && READ_ONCE(user->session_keyring)) { - kleave(" = 0 [exist]"); - return 0; - } + reg_keyring = get_user_register(user_ns); + if (IS_ERR(reg_keyring)) + return PTR_ERR(reg_keyring); - mutex_lock(&key_user_keyring_mutex); + down_write(&user_ns->keyring_sem); ret = 0; - if (!user->uid_keyring) { - /* get the UID-specific keyring - * - there may be one in existence already as it may have been - * pinned by a session, but the user_struct pointing to it - * may have been destroyed by setuid */ - sprintf(buf, "_uid.%u", uid); - - uid_keyring = find_keyring_by_name(buf, true); + /* Get the user keyring. Note that there may be one in existence + * already as it may have been pinned by a session, but the user_struct + * pointing to it may have been destroyed by setuid. + */ + sprintf(buf, "_uid.%u", uid); + uid_keyring_r = keyring_search(make_key_ref(reg_keyring, true), + &key_type_keyring, buf, false); + kdebug("_uid %p", uid_keyring_r); + if (uid_keyring_r == ERR_PTR(-EAGAIN)) { + uid_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID, + cred, user_keyring_perm, + KEY_ALLOC_UID_KEYRING | + KEY_ALLOC_IN_QUOTA, + NULL, reg_keyring); if (IS_ERR(uid_keyring)) { - uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID, - cred, user_keyring_perm, - KEY_ALLOC_UID_KEYRING | - KEY_ALLOC_IN_QUOTA, - NULL, NULL); - if (IS_ERR(uid_keyring)) { - ret = PTR_ERR(uid_keyring); - goto error; - } + ret = PTR_ERR(uid_keyring); + goto error; } + } else if (IS_ERR(uid_keyring_r)) { + ret = PTR_ERR(uid_keyring_r); + goto error; + } else { + uid_keyring = key_ref_to_ptr(uid_keyring_r); + } - /* get a default session keyring (which might also exist - * already) */ - sprintf(buf, "_uid_ses.%u", uid); - - session_keyring = find_keyring_by_name(buf, true); + /* Get a default session keyring (which might also exist already) */ + sprintf(buf, "_uid_ses.%u", uid); + session_keyring_r = keyring_search(make_key_ref(reg_keyring, true), + &key_type_keyring, buf, false); + kdebug("_uid_ses %p", session_keyring_r); + if (session_keyring_r == ERR_PTR(-EAGAIN)) { + session_keyring = keyring_alloc(buf, cred->user->uid, INVALID_GID, + cred, user_keyring_perm, + KEY_ALLOC_UID_KEYRING | + KEY_ALLOC_IN_QUOTA, + NULL, NULL); if (IS_ERR(session_keyring)) { - session_keyring = - keyring_alloc(buf, user->uid, INVALID_GID, - cred, user_keyring_perm, - KEY_ALLOC_UID_KEYRING | - KEY_ALLOC_IN_QUOTA, - NULL, NULL); - if (IS_ERR(session_keyring)) { - ret = PTR_ERR(session_keyring); - goto error_release; - } - - /* we install a link from the user session keyring to - * the user keyring */ - ret = key_link(session_keyring, uid_keyring); - if (ret < 0) - goto error_release_both; + ret = PTR_ERR(session_keyring); + goto error_release; } - /* install the keyrings */ - /* paired with READ_ONCE() */ - smp_store_release(&user->uid_keyring, uid_keyring); - /* paired with READ_ONCE() */ - smp_store_release(&user->session_keyring, session_keyring); + /* We install a link from the user session keyring to + * the user keyring. + */ + ret = key_link(session_keyring, uid_keyring); + if (ret < 0) + goto error_release_session; + + /* And only then link the user-session keyring to the + * register. + */ + ret = key_link(reg_keyring, session_keyring); + if (ret < 0) + goto error_release_session; + } else if (IS_ERR(session_keyring_r)) { + ret = PTR_ERR(session_keyring_r); + goto error_release; + } else { + session_keyring = key_ref_to_ptr(session_keyring_r); } - mutex_unlock(&key_user_keyring_mutex); + up_write(&user_ns->keyring_sem); + + if (_user_session_keyring) + *_user_session_keyring = session_keyring; + else + key_put(session_keyring); + if (_user_keyring) + *_user_keyring = uid_keyring; + else + key_put(uid_keyring); kleave(" = 0"); return 0; -error_release_both: +error_release_session: key_put(session_keyring); error_release: key_put(uid_keyring); error: - mutex_unlock(&key_user_keyring_mutex); + up_write(&user_ns->keyring_sem); kleave(" = %d", ret); return ret; } +/* + * Get the user session keyring if it exists, but don't create it if it + * doesn't. + */ +struct key *get_user_session_keyring(void) +{ + const struct cred *cred = current_cred(); + struct user_namespace *user_ns = current_user_ns(); + struct key *reg_keyring = user_ns->user_keyring_register; + key_ref_t session_keyring_r; + char buf[20]; + + if (!reg_keyring) + return NULL; + + sprintf(buf, "_uid_ses.%u", from_kuid(user_ns, cred->user->uid)); + + session_keyring_r = keyring_search(make_key_ref(reg_keyring, true), + &key_type_keyring, buf, false); + if (IS_ERR(session_keyring_r)) + return NULL; + return key_ref_to_ptr(session_keyring_r); +} + /* * Install a thread keyring to the given credentials struct if it didn't have * one already. This is allowed to overrun the quota. @@ -341,6 +414,7 @@ void key_fsgid_changed(struct task_struct *tsk) */ key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx) { + struct key *user_session; key_ref_t key_ref, ret, err; const struct cred *cred = ctx->cred; @@ -416,10 +490,9 @@ key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx) } } /* or search the user-session keyring */ - else if (READ_ONCE(cred->user->session_keyring)) { - key_ref = keyring_search_aux( - make_key_ref(READ_ONCE(cred->user->session_keyring), 1), - ctx); + else if ((user_session = get_user_session_keyring())) { + key_ref = keyring_search_aux(make_key_ref(user_session, 1), + ctx); if (!IS_ERR(key_ref)) goto found; @@ -435,6 +508,8 @@ key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx) err = key_ref; break; } + + key_put(user_session); } /* no key - decide on the error we're going to go for */ @@ -544,7 +619,7 @@ key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags, KEYRING_SEARCH_RECURSE), }; struct request_key_auth *rka; - struct key *key; + struct key *key, *user_session; key_ref_t key_ref, skey_ref; int ret; @@ -593,20 +668,20 @@ key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags, if (!ctx.cred->session_keyring) { /* always install a session keyring upon access if one * doesn't exist yet */ - ret = install_user_keyrings(); + ret = look_up_user_keyrings(NULL, &user_session); if (ret < 0) goto error; if (lflags & KEY_LOOKUP_CREATE) ret = join_session_keyring(NULL); else - ret = install_session_keyring( - ctx.cred->user->session_keyring); + ret = install_session_keyring(user_session); + key_put(user_session); if (ret < 0) goto error; goto reget_creds; - } else if (ctx.cred->session_keyring == - READ_ONCE(ctx.cred->user->session_keyring) && + } else if (test_bit(KEY_FLAG_UID_KEYRING, + &ctx.cred->session_keyring->flags) && lflags & KEY_LOOKUP_CREATE) { ret = join_session_keyring(NULL); if (ret < 0) @@ -620,26 +695,16 @@ key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags, break; case KEY_SPEC_USER_KEYRING: - if (!READ_ONCE(ctx.cred->user->uid_keyring)) { - ret = install_user_keyrings(); - if (ret < 0) - goto error; - } - - key = ctx.cred->user->uid_keyring; - __key_get(key); + ret = look_up_user_keyrings(&key, NULL); + if (ret < 0) + goto error; key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_SESSION_KEYRING: - if (!READ_ONCE(ctx.cred->user->session_keyring)) { - ret = install_user_keyrings(); - if (ret < 0) - goto error; - } - - key = ctx.cred->user->session_keyring; - __key_get(key); + ret = look_up_user_keyrings(NULL, &key); + if (ret < 0) + goto error; key_ref = make_key_ref(key, 1); break; @@ -888,7 +953,7 @@ void key_change_session_keyring(struct callback_head *twork) */ static int __init init_root_keyring(void) { - return install_user_keyrings(); + return look_up_user_keyrings(NULL, NULL); } late_initcall(init_root_keyring); diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 39802540ffff..d95627888f5a 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -96,7 +96,7 @@ static int call_sbin_request_key(struct key *authkey, void *aux) struct request_key_auth *rka = get_request_key_auth(authkey); const struct cred *cred = current_cred(); key_serial_t prkey, sskey; - struct key *key = rka->target_key, *keyring, *session; + struct key *key = rka->target_key, *keyring, *session, *user_session; char *argv[9], *envp[3], uid_str[12], gid_str[12]; char key_str[12], keyring_str[3][12]; char desc[20]; @@ -104,9 +104,9 @@ static int call_sbin_request_key(struct key *authkey, void *aux) kenter("{%d},{%d},%s", key->serial, authkey->serial, rka->op); - ret = install_user_keyrings(); + ret = look_up_user_keyrings(NULL, &user_session); if (ret < 0) - goto error_alloc; + goto error_us; /* allocate a new session keyring */ sprintf(desc, "_req.%u", key->serial); @@ -144,7 +144,7 @@ static int call_sbin_request_key(struct key *authkey, void *aux) session = cred->session_keyring; if (!session) - session = cred->user->session_keyring; + session = user_session; sskey = session->serial; sprintf(keyring_str[2], "%d", sskey); @@ -187,6 +187,8 @@ static int call_sbin_request_key(struct key *authkey, void *aux) error_alloc: complete_request_key(authkey, ret); +error_us: + key_put(user_session); kleave(" = %d", ret); return ret; } @@ -289,16 +291,19 @@ static int construct_get_dest_keyring(struct key **_dest_keyring) if (dest_keyring) break; + /* Fall through */ /* fall through */ case KEY_REQKEY_DEFL_USER_SESSION_KEYRING: - dest_keyring = - key_get(READ_ONCE(cred->user->session_keyring)); + ret = look_up_user_keyrings(NULL, &dest_keyring); + if (ret < 0) + return ret; break; case KEY_REQKEY_DEFL_USER_KEYRING: - dest_keyring = - key_get(READ_ONCE(cred->user->uid_keyring)); + ret = look_up_user_keyrings(&dest_keyring, NULL); + if (ret < 0) + return ret; break; case KEY_REQKEY_DEFL_GROUP_KEYRING: