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KEYS: Fix an RCU warning in the reading of user keys

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Fix an RCU warning in the reading of user keys:

===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
security/keys/user_defined.c:202 invoked rcu_dereference_check() without protection!

other info that might help us debug this:

rcu_scheduler_active = 1, debug_locks = 0
1 lock held by keyctl/3637:
 #0:  (&key->sem){+++++.}, at: [<ffffffff811a80ae>] keyctl_read_key+0x9c/0xcf

stack backtrace:
Pid: 3637, comm: keyctl Not tainted 2.6.34-rc5-cachefs #18
Call Trace:
 [<ffffffff81051f6c>] lockdep_rcu_dereference+0xaa/0xb2
 [<ffffffff811aa55f>] user_read+0x47/0x91
 [<ffffffff811a80be>] keyctl_read_key+0xac/0xcf
 [<ffffffff811a8a06>] sys_keyctl+0x75/0xb7
 [<ffffffff81001eeb>] system_call_fastpath+0x16/0x1b

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
David Howells 2010-04-30 14:32:08 +01:00 committed by James Morris
parent a66f6375bd
commit d9a9b4aeea
1 changed files with 2 additions and 1 deletions
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3
security/keys/user_defined.c
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@ -199,7 +199,8 @@ long user_read(const struct key *key, char __user *buffer, size_t buflen)
struct user_key_payload *upayload;
long ret;
upayload = rcu_dereference(key->payload.data);
upayload = rcu_dereference_protected(
key->payload.data, rwsem_is_locked(&((struct key *)key)->sem));
ret = upayload->datalen;
/* we can return the data as is */