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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 06/10] keys: Hoist locking out of __key_link_begin() [ver #3] From: David Howells To: keyrings@vger.kernel.org, ebiggers@kernel.org Cc: dhowells@redhat.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 19 Jun 2019 14:19:32 +0100 Message-ID: <156095037291.9363.13087730114176092160.stgit@warthog.procyon.org.uk> In-Reply-To: <156095032052.9363.8954337545422131435.stgit@warthog.procyon.org.uk> References: <156095032052.9363.8954337545422131435.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Wed, 19 Jun 2019 13:19:35 +0000 (UTC) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Hoist the locking of out of __key_link_begin() and into its callers. This is necessary to allow the upcoming key_move() operation to correctly order taking of the source keyring semaphore, the destination keyring semaphore and the keyring serialisation lock. Signed-off-by: David Howells --- security/keys/internal.h | 2 + security/keys/key.c | 27 ++++++++++++--- security/keys/keyring.c | 78 ++++++++++++++++++++++++++----------------- security/keys/request_key.c | 7 +++- 4 files changed, 76 insertions(+), 38 deletions(-) diff --git a/security/keys/internal.h b/security/keys/internal.h index 8f533c81aa8d..25cdd0cbdc06 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -93,6 +93,8 @@ extern wait_queue_head_t request_key_conswq; extern struct key_type *key_type_lookup(const char *type); extern void key_type_put(struct key_type *ktype); +extern int __key_link_lock(struct key *keyring, + const struct keyring_index_key *index_key); extern int __key_link_begin(struct key *keyring, const struct keyring_index_key *index_key, struct assoc_array_edit **_edit); diff --git a/security/keys/key.c b/security/keys/key.c index 696f1c092c50..bba71acec886 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -500,7 +500,7 @@ int key_instantiate_and_link(struct key *key, struct key *authkey) { struct key_preparsed_payload prep; - struct assoc_array_edit *edit; + struct assoc_array_edit *edit = NULL; int ret; memset(&prep, 0, sizeof(prep)); @@ -515,10 +515,14 @@ int key_instantiate_and_link(struct key *key, } if (keyring) { - ret = __key_link_begin(keyring, &key->index_key, &edit); + ret = __key_link_lock(keyring, &key->index_key); if (ret < 0) goto error; + ret = __key_link_begin(keyring, &key->index_key, &edit); + if (ret < 0) + goto error_link_end; + if (keyring->restrict_link && keyring->restrict_link->check) { struct key_restriction *keyres = keyring->restrict_link; @@ -570,7 +574,7 @@ int key_reject_and_link(struct key *key, struct key *keyring, struct key *authkey) { - struct assoc_array_edit *edit; + struct assoc_array_edit *edit = NULL; int ret, awaken, link_ret = 0; key_check(key); @@ -583,7 +587,12 @@ int key_reject_and_link(struct key *key, if (keyring->restrict_link) return -EPERM; - link_ret = __key_link_begin(keyring, &key->index_key, &edit); + link_ret = __key_link_lock(keyring, &key->index_key); + if (link_ret == 0) { + link_ret = __key_link_begin(keyring, &key->index_key, &edit); + if (link_ret < 0) + __key_link_end(keyring, &key->index_key, edit); + } } mutex_lock(&key_construction_mutex); @@ -810,7 +819,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref, .description = description, }; struct key_preparsed_payload prep; - struct assoc_array_edit *edit; + struct assoc_array_edit *edit = NULL; const struct cred *cred = current_cred(); struct key *keyring, *key = NULL; key_ref_t key_ref; @@ -860,12 +869,18 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref, } index_key.desc_len = strlen(index_key.description); - ret = __key_link_begin(keyring, &index_key, &edit); + ret = __key_link_lock(keyring, &index_key); if (ret < 0) { key_ref = ERR_PTR(ret); goto error_free_prep; } + ret = __key_link_begin(keyring, &index_key, &edit); + if (ret < 0) { + key_ref = ERR_PTR(ret); + goto error_link_end; + } + if (restrict_link && restrict_link->check) { ret = restrict_link->check(keyring, index_key.type, &prep.payload, restrict_link->key); diff --git a/security/keys/keyring.c b/security/keys/keyring.c index 6990c7761eaa..12acad3db6cf 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -1199,14 +1199,34 @@ static int keyring_detect_cycle(struct key *A, struct key *B) return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result); } +/* + * Lock keyring for link. + */ +int __key_link_lock(struct key *keyring, + const struct keyring_index_key *index_key) + __acquires(&keyring->sem) + __acquires(&keyring_serialise_link_lock) +{ + if (keyring->type != &key_type_keyring) + return -ENOTDIR; + + down_write(&keyring->sem); + + /* Serialise link/link calls to prevent parallel calls causing a cycle + * when linking two keyring in opposite orders. + */ + if (index_key->type == &key_type_keyring) + mutex_lock(&keyring_serialise_link_lock); + + return 0; +} + /* * Preallocate memory so that a key can be linked into to a keyring. */ int __key_link_begin(struct key *keyring, const struct keyring_index_key *index_key, struct assoc_array_edit **_edit) - __acquires(&keyring->sem) - __acquires(&keyring_serialise_link_lock) { struct assoc_array_edit *edit; int ret; @@ -1215,20 +1235,13 @@ int __key_link_begin(struct key *keyring, keyring->serial, index_key->type->name, index_key->description); BUG_ON(index_key->desc_len == 0); + BUG_ON(*_edit != NULL); - if (keyring->type != &key_type_keyring) - return -ENOTDIR; - - down_write(&keyring->sem); + *_edit = NULL; ret = -EKEYREVOKED; if (test_bit(KEY_FLAG_REVOKED, &keyring->flags)) - goto error_krsem; - - /* serialise link/link calls to prevent parallel calls causing a cycle - * when linking two keyring in opposite orders */ - if (index_key->type == &key_type_keyring) - mutex_lock(&keyring_serialise_link_lock); + goto error; /* Create an edit script that will insert/replace the key in the * keyring tree. @@ -1239,7 +1252,7 @@ int __key_link_begin(struct key *keyring, NULL); if (IS_ERR(edit)) { ret = PTR_ERR(edit); - goto error_sem; + goto error; } /* If we're not replacing a link in-place then we're going to need some @@ -1258,11 +1271,7 @@ int __key_link_begin(struct key *keyring, error_cancel: assoc_array_cancel_edit(edit); -error_sem: - if (index_key->type == &key_type_keyring) - mutex_unlock(&keyring_serialise_link_lock); -error_krsem: - up_write(&keyring->sem); +error: kleave(" = %d", ret); return ret; } @@ -1312,9 +1321,6 @@ void __key_link_end(struct key *keyring, BUG_ON(index_key->type == NULL); kenter("%d,%s,", keyring->serial, index_key->type->name); - if (index_key->type == &key_type_keyring) - mutex_unlock(&keyring_serialise_link_lock); - if (edit) { if (!edit->dead_leaf) { key_payload_reserve(keyring, @@ -1323,6 +1329,9 @@ void __key_link_end(struct key *keyring, assoc_array_cancel_edit(edit); } up_write(&keyring->sem); + + if (index_key->type == &key_type_keyring) + mutex_unlock(&keyring_serialise_link_lock); } /* @@ -1358,7 +1367,7 @@ static int __key_link_check_restriction(struct key *keyring, struct key *key) */ int key_link(struct key *keyring, struct key *key) { - struct assoc_array_edit *edit; + struct assoc_array_edit *edit = NULL; int ret; kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage)); @@ -1366,17 +1375,24 @@ int key_link(struct key *keyring, struct key *key) key_check(keyring); key_check(key); + ret = __key_link_lock(keyring, &key->index_key); + if (ret < 0) + goto error; + ret = __key_link_begin(keyring, &key->index_key, &edit); - if (ret == 0) { - kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage)); - ret = __key_link_check_restriction(keyring, key); - if (ret == 0) - ret = __key_link_check_live_key(keyring, key); - if (ret == 0) - __key_link(key, &edit); - __key_link_end(keyring, &key->index_key, edit); - } + if (ret < 0) + goto error_end; + + kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage)); + ret = __key_link_check_restriction(keyring, key); + if (ret == 0) + ret = __key_link_check_live_key(keyring, key); + if (ret == 0) + __key_link(key, &edit); +error_end: + __key_link_end(keyring, &key->index_key, edit); +error: kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage)); return ret; } diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 1f234b019437..857da65e1940 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -343,7 +343,7 @@ static int construct_alloc_key(struct keyring_search_context *ctx, struct key_user *user, struct key **_key) { - struct assoc_array_edit *edit; + struct assoc_array_edit *edit = NULL; struct key *key; key_perm_t perm; key_ref_t key_ref; @@ -372,6 +372,9 @@ static int construct_alloc_key(struct keyring_search_context *ctx, set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags); if (dest_keyring) { + ret = __key_link_lock(dest_keyring, &ctx->index_key); + if (ret < 0) + goto link_lock_failed; ret = __key_link_begin(dest_keyring, &ctx->index_key, &edit); if (ret < 0) goto link_prealloc_failed; @@ -423,6 +426,8 @@ static int construct_alloc_key(struct keyring_search_context *ctx, return ret; link_prealloc_failed: + __key_link_end(dest_keyring, &ctx->index_key, edit); +link_lock_failed: mutex_unlock(&user->cons_lock); key_put(key); kleave(" = %d [prelink]", ret);