![David Howells](/assets/img/avatar_default.png)
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: [<d000000002527abc>] 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 <jstancek@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Jan Stancek <jstancek@redhat.com> Signed-off-by: James Morris <james.l.morris@oracle.com>
205 lines
4.6 KiB
C
205 lines
4.6 KiB
C
/* user_defined.c: user defined key type
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/seq_file.h>
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#include <linux/err.h>
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#include <keys/user-type.h>
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#include <linux/uaccess.h>
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#include "internal.h"
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static int logon_vet_description(const char *desc);
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/*
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* user defined keys take an arbitrary string as the description and an
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* arbitrary blob of data as the payload
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*/
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struct key_type key_type_user = {
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.name = "user",
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.preparse = user_preparse,
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.free_preparse = user_free_preparse,
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.instantiate = generic_key_instantiate,
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.update = user_update,
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.revoke = user_revoke,
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.destroy = user_destroy,
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.describe = user_describe,
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.read = user_read,
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};
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EXPORT_SYMBOL_GPL(key_type_user);
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/*
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* This key type is essentially the same as key_type_user, but it does
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* not define a .read op. This is suitable for storing username and
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* password pairs in the keyring that you do not want to be readable
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* from userspace.
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*/
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struct key_type key_type_logon = {
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.name = "logon",
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.preparse = user_preparse,
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.free_preparse = user_free_preparse,
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.instantiate = generic_key_instantiate,
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.update = user_update,
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.revoke = user_revoke,
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.destroy = user_destroy,
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.describe = user_describe,
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.vet_description = logon_vet_description,
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};
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EXPORT_SYMBOL_GPL(key_type_logon);
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/*
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* Preparse a user defined key payload
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*/
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int user_preparse(struct key_preparsed_payload *prep)
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{
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struct user_key_payload *upayload;
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size_t datalen = prep->datalen;
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if (datalen <= 0 || datalen > 32767 || !prep->data)
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return -EINVAL;
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upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
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if (!upayload)
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return -ENOMEM;
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/* attach the data */
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prep->quotalen = datalen;
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prep->payload.data[0] = upayload;
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upayload->datalen = datalen;
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memcpy(upayload->data, prep->data, datalen);
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return 0;
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}
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EXPORT_SYMBOL_GPL(user_preparse);
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/*
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* Free a preparse of a user defined key payload
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*/
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void user_free_preparse(struct key_preparsed_payload *prep)
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{
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kfree(prep->payload.data[0]);
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}
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EXPORT_SYMBOL_GPL(user_free_preparse);
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/*
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* update a user defined key
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* - the key's semaphore is write-locked
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*/
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int user_update(struct key *key, struct key_preparsed_payload *prep)
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{
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struct user_key_payload *zap = NULL;
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int ret;
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/* check the quota and attach the new data */
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ret = key_payload_reserve(key, prep->datalen);
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if (ret < 0)
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return ret;
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/* attach the new data, displacing the old */
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key->expiry = prep->expiry;
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if (!test_bit(KEY_FLAG_NEGATIVE, &key->flags))
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zap = dereference_key_locked(key);
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rcu_assign_keypointer(key, prep->payload.data[0]);
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prep->payload.data[0] = NULL;
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if (zap)
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kfree_rcu(zap, rcu);
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return ret;
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}
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EXPORT_SYMBOL_GPL(user_update);
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/*
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* dispose of the links from a revoked keyring
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* - called with the key sem write-locked
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*/
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void user_revoke(struct key *key)
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{
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struct user_key_payload *upayload = user_key_payload_locked(key);
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/* clear the quota */
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key_payload_reserve(key, 0);
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if (upayload) {
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rcu_assign_keypointer(key, NULL);
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kfree_rcu(upayload, rcu);
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}
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}
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EXPORT_SYMBOL(user_revoke);
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/*
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* dispose of the data dangling from the corpse of a user key
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*/
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void user_destroy(struct key *key)
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{
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struct user_key_payload *upayload = key->payload.data[0];
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kfree(upayload);
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}
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EXPORT_SYMBOL_GPL(user_destroy);
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/*
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* describe the user key
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*/
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void user_describe(const struct key *key, struct seq_file *m)
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{
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seq_puts(m, key->description);
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if (key_is_instantiated(key))
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seq_printf(m, ": %u", key->datalen);
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}
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EXPORT_SYMBOL_GPL(user_describe);
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/*
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* read the key data
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* - the key's semaphore is read-locked
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*/
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long user_read(const struct key *key, char __user *buffer, size_t buflen)
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{
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const struct user_key_payload *upayload;
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long ret;
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upayload = user_key_payload_locked(key);
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ret = upayload->datalen;
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/* we can return the data as is */
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if (buffer && buflen > 0) {
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if (buflen > upayload->datalen)
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buflen = upayload->datalen;
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if (copy_to_user(buffer, upayload->data, buflen) != 0)
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ret = -EFAULT;
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}
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return ret;
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}
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EXPORT_SYMBOL_GPL(user_read);
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/* Vet the description for a "logon" key */
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static int logon_vet_description(const char *desc)
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{
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char *p;
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/* require a "qualified" description string */
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p = strchr(desc, ':');
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if (!p)
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return -EINVAL;
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/* also reject description with ':' as first char */
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if (p == desc)
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return -EINVAL;
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return 0;
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}
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