From 0837e49ab3fa8d903a499984575d71efee8097ce Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 1 Mar 2017 15:11:23 +0000 Subject: KEYS: Differentiate uses of rcu_dereference_key() and user_key_payload() rcu_dereference_key() and user_key_payload() are currently being used in two different, incompatible ways: (1) As a wrapper to rcu_dereference() - when only the RCU read lock used to protect the key. (2) As a wrapper to rcu_dereference_protected() - when the key semaphor is used to protect the key and the may be being modified. Fix this by splitting both of the key wrappers to produce: (1) RCU accessors for keys when caller has the key semaphore locked: dereference_key_locked() user_key_payload_locked() (2) RCU accessors for keys when caller holds the RCU read lock: dereference_key_rcu() user_key_payload_rcu() This should fix following warning in the NFS idmapper =============================== [ INFO: suspicious RCU usage. ] 4.10.0 #1 Tainted: G W ------------------------------- ./include/keys/user-type.h:53 suspicious rcu_dereference_protected() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 0 1 lock held by mount.nfs/5987: #0: (rcu_read_lock){......}, at: [] nfs_idmap_get_key+0x15c/0x420 [nfsv4] stack backtrace: CPU: 1 PID: 5987 Comm: mount.nfs Tainted: G W 4.10.0 #1 Call Trace: dump_stack+0xe8/0x154 (unreliable) lockdep_rcu_suspicious+0x140/0x190 nfs_idmap_get_key+0x380/0x420 [nfsv4] nfs_map_name_to_uid+0x2a0/0x3b0 [nfsv4] decode_getfattr_attrs+0xfac/0x16b0 [nfsv4] decode_getfattr_generic.constprop.106+0xbc/0x150 [nfsv4] nfs4_xdr_dec_lookup_root+0xac/0xb0 [nfsv4] rpcauth_unwrap_resp+0xe8/0x140 [sunrpc] call_decode+0x29c/0x910 [sunrpc] __rpc_execute+0x140/0x8f0 [sunrpc] rpc_run_task+0x170/0x200 [sunrpc] nfs4_call_sync_sequence+0x68/0xa0 [nfsv4] _nfs4_lookup_root.isra.44+0xd0/0xf0 [nfsv4] nfs4_lookup_root+0xe0/0x350 [nfsv4] nfs4_lookup_root_sec+0x70/0xa0 [nfsv4] nfs4_find_root_sec+0xc4/0x100 [nfsv4] nfs4_proc_get_rootfh+0x5c/0xf0 [nfsv4] nfs4_get_rootfh+0x6c/0x190 [nfsv4] nfs4_server_common_setup+0xc4/0x260 [nfsv4] nfs4_create_server+0x278/0x3c0 [nfsv4] nfs4_remote_mount+0x50/0xb0 [nfsv4] mount_fs+0x74/0x210 vfs_kern_mount+0x78/0x220 nfs_do_root_mount+0xb0/0x140 [nfsv4] nfs4_try_mount+0x60/0x100 [nfsv4] nfs_fs_mount+0x5ec/0xda0 [nfs] mount_fs+0x74/0x210 vfs_kern_mount+0x78/0x220 do_mount+0x254/0xf70 SyS_mount+0x94/0x100 system_call+0x38/0xe0 Reported-by: Jan Stancek Signed-off-by: David Howells Tested-by: Jan Stancek Signed-off-by: James Morris --- security/keys/dh.c | 2 +- security/keys/encrypted-keys/encrypted.c | 4 ++-- security/keys/trusted.c | 4 ++-- security/keys/user_defined.c | 6 +++--- 4 files changed, 8 insertions(+), 8 deletions(-) (limited to 'security/keys') 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 @@ out: 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 */ -- cgit v1.2.3