[0/2] key payload access with just rcu_read_lock()

Message ID	20283.1488277729@warthog.procyon.org.uk (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-nfs-owner@kernel.org> Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells <dhowells@redhat.com> In-Reply-To: <25524.1488241404@warthog.procyon.org.uk> References: <25524.1488241404@warthog.procyon.org.uk> <343033867.485297.1488235638227.JavaMail.zimbra@redhat.com> <cover.1487802542.git.jstancek@redhat.com> <9557.1488233061@warthog.procyon.org.uk> To: Jan Stancek <jstancek@redhat.com> Cc: dhowells@redhat.com, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, bcodding@redhat.com, asavkov@redhat.com Subject: Re: [PATCH 0/2] key payload access with just rcu_read_lock() MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <20282.1488277729.1@warthog.procyon.org.uk> Content-Transfer-Encoding: 8BIT Date: Tue, 28 Feb 2017 10:28:49 +0000 Message-ID: <20283.1488277729@warthog.procyon.org.uk> Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk

diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt index 3849814bfe6d..0e03baf271bd 100644 --- a/Documentation/security/keys.txt +++ b/Documentation/security/keys.txt @@ -1151,8 +1151,21 @@ access the data: usage. This is called key->payload.rcu_data0. The following accessors wrap the RCU calls to this element: - rcu_assign_keypointer(struct key *key, void *data); - void *rcu_dereference_key(struct key *key); + (a) Set or change the first payload pointer: + + rcu_assign_keypointer(struct key *key, void *data); + + (b) Read the first payload pointer with the key semaphore held: + + [const] void *dereference_key_locked([const] struct key *key); + + Note that the return value will inherit its constness from the key + parameter. Static analysis will give an error if it things the lock + isn't held. + + (c) Read the first payload pointer with the RCU read lock held: + + const void *dereference_key_rcu(const struct key *key); =================== diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c index 1cb2ca9dfae3..389a3637ffcc 100644 --- a/drivers/md/dm-crypt.c +++ b/drivers/md/dm-crypt.c @@ -1536,7 +1536,7 @@ static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string down_read(&key->sem); - ukp = user_key_payload(key); + ukp = user_key_payload_locked(key); if (!ukp) { up_read(&key->sem); key_put(key); diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 777ad9f4fc3c..8a3ecef30d3c 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -2455,7 +2455,7 @@ cifs_set_cifscreds(struct smb_vol *vol, struct cifs_ses *ses) } down_read(&key->sem); - upayload = user_key_payload(key); + upayload = user_key_payload_locked(key); if (IS_ERR_OR_NULL(upayload)) { rc = upayload ? PTR_ERR(upayload) : -EINVAL; goto out_key_put; diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c index 02eb6b9e4438..d5d896fa5a71 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -103,7 +103,7 @@ static int validate_user_key(struct fscrypt_info *crypt_info, goto out; } down_read(&keyring_key->sem); - ukp = user_key_payload(keyring_key); + ukp = user_key_payload_locked(keyring_key); if (ukp->datalen != sizeof(struct fscrypt_key)) { res = -EINVAL; up_read(&keyring_key->sem); diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h index 599a29237cfe..95c1c8d34539 100644 --- a/fs/ecryptfs/ecryptfs_kernel.h +++ b/fs/ecryptfs/ecryptfs_kernel.h @@ -117,7 +117,7 @@ ecryptfs_get_key_payload_data(struct key *key) auth_tok = ecryptfs_get_encrypted_key_payload_data(key); if (!auth_tok) - return (struct ecryptfs_auth_tok *)user_key_payload(key)->data; + return (struct ecryptfs_auth_tok *)user_key_payload_locked(key)->data; else return auth_tok; } diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c index 5d5ddaa84b21..67f940892ef8 100644 --- a/fs/fscache/object-list.c +++ b/fs/fscache/object-list.c @@ -329,7 +329,7 @@ static void fscache_objlist_config(struct fscache_objlist_data *data) config = 0; rcu_read_lock(); - confkey = user_key_payload(key); + confkey = user_key_payload_rcu(key); buf = confkey->data; for (len = confkey->datalen - 1; len >= 0; len--) { diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c index c444285bb1b1..835c163f61af 100644 --- a/fs/nfs/nfs4idmap.c +++ b/fs/nfs/nfs4idmap.c @@ -316,7 +316,7 @@ static ssize_t nfs_idmap_get_key(const char *name, size_t namelen, if (ret < 0) goto out_up; - payload = user_key_payload(rkey); + payload = user_key_payload_rcu(rkey); if (IS_ERR_OR_NULL(payload)) { ret = PTR_ERR(payload); goto out_up; diff --git a/include/keys/user-type.h b/include/keys/user-type.h index c56fef40f53e..e098cbe27db5 100644 --- a/include/keys/user-type.h +++ b/include/keys/user-type.h @@ -48,9 +48,14 @@ extern void user_describe(const struct key *user, struct seq_file *m); extern long user_read(const struct key *key, char __user *buffer, size_t buflen); -static inline const struct user_key_payload *user_key_payload(const struct key *key) +static inline const struct user_key_payload *user_key_payload_rcu(const struct key *key) { - return (struct user_key_payload *)rcu_dereference_key(key); + return (struct user_key_payload *)dereference_key_rcu(key); +} + +static inline struct user_key_payload *user_key_payload_locked(const struct key *key) +{ + return (struct user_key_payload *)dereference_key_locked((struct key *)key); } #endif /* CONFIG_KEYS */ diff --git a/include/linux/key.h b/include/linux/key.h index 722914798f37..e45212f2777e 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -354,7 +354,10 @@ static inline bool key_is_instantiated(const struct key *key) !test_bit(KEY_FLAG_NEGATIVE, &key->flags); } -#define rcu_dereference_key(KEY) \ +#define dereference_key_rcu(KEY) \ + (rcu_dereference((KEY)->payload.rcu_data0)) + +#define dereference_key_locked(KEY) \ (rcu_dereference_protected((KEY)->payload.rcu_data0, \ rwsem_is_locked(&((struct key *)(KEY))->sem))) diff --git a/lib/digsig.c b/lib/digsig.c index 55b8b2f41a9e..03d7c63837ae 100644 --- a/lib/digsig.c +++ b/lib/digsig.c @@ -85,7 +85,7 @@ static int digsig_verify_rsa(struct key *key, struct pubkey_hdr *pkh; down_read(&key->sem); - ukp = user_key_payload(key); + ukp = user_key_payload_locked(key); if (ukp->datalen < sizeof(*pkh)) goto err1; diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c index ecc28cff08ab..d502c94b1a82 100644 --- a/net/dns_resolver/dns_query.c +++ b/net/dns_resolver/dns_query.c @@ -70,7 +70,7 @@ int dns_query(const char *type, const char *name, size_t namelen, const char *options, char **_result, time64_t *_expiry) { struct key *rkey; - const struct user_key_payload *upayload; + struct user_key_payload *upayload; const struct cred *saved_cred; size_t typelen, desclen; char *desc, *cp; @@ -141,7 +141,7 @@ int dns_query(const char *type, const char *name, size_t namelen, if (ret) goto put; - upayload = user_key_payload(rkey); + upayload = user_key_payload_locked(rkey); len = upayload->datalen; ret = -ENOMEM; diff --git a/security/keys/dh.c b/security/keys/dh.c index 531ed2ec132f..893af4c45038 100644 --- a/security/keys/dh.c +++ b/security/keys/dh.c @@ -55,7 +55,7 @@ static ssize_t mpi_from_key(key_serial_t keyid, size_t maxlen, MPI *mpi) if (status == 0) { const struct user_key_payload *payload; - payload = user_key_payload(key); + payload = user_key_payload_locked(key); if (maxlen == 0) { *mpi = NULL; diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index 4fb315cddf5b..0010955d7876 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -314,7 +314,7 @@ static struct key *request_user_key(const char *master_desc, const u8 **master_k goto error; down_read(&ukey->sem); - upayload = user_key_payload(ukey); + upayload = user_key_payload_locked(ukey); *master_key = upayload->data; *master_keylen = upayload->datalen; error: @@ -926,7 +926,7 @@ static long encrypted_read(const struct key *key, char __user *buffer, size_t asciiblob_len; int ret; - epayload = rcu_dereference_key(key); + epayload = dereference_key_locked(key); /* returns the hex encoded iv, encrypted-data, and hmac as ascii */ asciiblob_len = epayload->datablob_len + ivsize + 1 diff --git a/security/keys/trusted.c b/security/keys/trusted.c index 90d61751ff12..2ae31c5a87de 100644 --- a/security/keys/trusted.c +++ b/security/keys/trusted.c @@ -1140,12 +1140,12 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep) static long trusted_read(const struct key *key, char __user *buffer, size_t buflen) { - struct trusted_key_payload *p; + const struct trusted_key_payload *p; char *ascii_buf; char *bufp; int i; - p = rcu_dereference_key(key); + p = dereference_key_locked(key); if (!p) return -EINVAL; if (!buffer || buflen <= 0) diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c index e187c8909d9d..26605134f17a 100644 --- a/security/keys/user_defined.c +++ b/security/keys/user_defined.c @@ -107,7 +107,7 @@ int user_update(struct key *key, struct key_preparsed_payload *prep) /* attach the new data, displacing the old */ key->expiry = prep->expiry; if (!test_bit(KEY_FLAG_NEGATIVE, &key->flags)) - zap = rcu_dereference_key(key); + zap = dereference_key_locked(key); rcu_assign_keypointer(key, prep->payload.data[0]); prep->payload.data[0] = NULL; @@ -123,7 +123,7 @@ EXPORT_SYMBOL_GPL(user_update); */ void user_revoke(struct key *key) { - struct user_key_payload *upayload = key->payload.data[0]; + struct user_key_payload *upayload = user_key_payload_locked(key); /* clear the quota */ key_payload_reserve(key, 0); @@ -169,7 +169,7 @@ long user_read(const struct key *key, char __user *buffer, size_t buflen) const struct user_key_payload *upayload; long ret; - upayload = user_key_payload(key); + upayload = user_key_payload_locked(key); ret = upayload->datalen; /* we can return the data as is */

[0/2] key payload access with just rcu_read_lock()

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