0837e49ab3
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>
63 lines
2.1 KiB
C
63 lines
2.1 KiB
C
/* user-type.h: User-defined key type
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*
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* Copyright (C) 2005 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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#ifndef _KEYS_USER_TYPE_H
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#define _KEYS_USER_TYPE_H
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#include <linux/key.h>
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#include <linux/rcupdate.h>
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#ifdef CONFIG_KEYS
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/*****************************************************************************/
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/*
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* the payload for a key of type "user" or "logon"
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* - once filled in and attached to a key:
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* - the payload struct is invariant may not be changed, only replaced
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* - the payload must be read with RCU procedures or with the key semaphore
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* held
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* - the payload may only be replaced with the key semaphore write-locked
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* - the key's data length is the size of the actual data, not including the
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* payload wrapper
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*/
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struct user_key_payload {
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struct rcu_head rcu; /* RCU destructor */
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unsigned short datalen; /* length of this data */
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char data[0]; /* actual data */
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};
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extern struct key_type key_type_user;
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extern struct key_type key_type_logon;
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struct key_preparsed_payload;
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extern int user_preparse(struct key_preparsed_payload *prep);
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extern void user_free_preparse(struct key_preparsed_payload *prep);
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extern int user_update(struct key *key, struct key_preparsed_payload *prep);
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extern void user_revoke(struct key *key);
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extern void user_destroy(struct key *key);
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extern void user_describe(const struct key *user, struct seq_file *m);
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extern long user_read(const struct key *key,
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char __user *buffer, size_t buflen);
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static inline const struct user_key_payload *user_key_payload_rcu(const struct key *key)
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{
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return (struct user_key_payload *)dereference_key_rcu(key);
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}
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static inline struct user_key_payload *user_key_payload_locked(const struct key *key)
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{
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return (struct user_key_payload *)dereference_key_locked((struct key *)key);
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}
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#endif /* CONFIG_KEYS */
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#endif /* _KEYS_USER_TYPE_H */
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