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authorDavid Howells <dhowells@redhat.com>2012-05-11 10:56:56 +0100
committerDavid Howells <dhowells@redhat.com>2012-05-11 10:56:56 +0100
commit65d87fe68abf2fc226a9e96be61160f65d6b4680 (patch)
tree23881b6daf54c7522178363f0ae32ddb6c836784 /include
parent1eb1bcf5bfad001128293b86d891c9d6f2f27333 (diff)
KEYS: Perform RCU synchronisation on keys prior to key destruction
Make the keys garbage collector invoke synchronize_rcu() prior to destroying keys with a zero usage count. This means that a key can be examined under the RCU read lock in the safe knowledge that it won't get deallocated until after the lock is released - even if its usage count becomes zero whilst we're looking at it. This is useful in keyring search vs key link. Consider a keyring containing a link to a key. That link can be replaced in-place in the keyring without requiring an RCU copy-and-replace on the keyring contents without breaking a search underway on that keyring when the displaced key is released, provided the key is actually destroyed only after the RCU read lock held by the search algorithm is released. This permits __key_link() to replace a key without having to reallocate the key payload. A key gets replaced if a new key being linked into a keyring has the same type and description. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Jeff Layton <jlayton@redhat.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/key.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/key.h b/include/linux/key.h
index 96933b1e5d24..c505f83c9691 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -124,7 +124,10 @@ static inline unsigned long is_key_possessed(const key_ref_t key_ref)
struct key {
atomic_t usage; /* number of references */
key_serial_t serial; /* key serial number */
- struct rb_node serial_node;
+ union {
+ struct list_head graveyard_link;
+ struct rb_node serial_node;
+ };
struct key_type *type; /* type of key */
struct rw_semaphore sem; /* change vs change sem */
struct key_user *user; /* owner of this key */

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