KEYS: Fix RCU handling in key_gc_keyring()
authorDavid Howells <dhowells@redhat.com>
Tue, 4 May 2010 13:16:10 +0000 (14:16 +0100)
committerJames Morris <jmorris@namei.org>
Wed, 5 May 2010 01:39:23 +0000 (11:39 +1000)
commitcf8304e8f380903de3a15dc6ebd551c9e6cf1a21
treefe94f3ebb044b5026b1062631b2d89e77c8b674e
parentd9a9b4aeea334e7912ce3d878d7f5cc6fdf1ffe4
KEYS: Fix RCU handling in key_gc_keyring()

key_gc_keyring() needs to either hold the RCU read lock or hold the keyring
semaphore if it's going to scan the keyring's list.  Given that it only needs
to read the key list, and it's doing so under a spinlock, the RCU read lock is
the thing to use.

Furthermore, the RCU check added in e7b0a61b7929632d36cf052d9e2820ef0a9c1bfe is
incorrect as holding the spinlock on key_serial_lock is not grounds for
assuming a keyring's pointer list can be read safely.  Instead, a simple
rcu_dereference() inside of the previously mentioned RCU read lock is what we
want.

Reported-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>
security/keys/gc.c