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    Subject[tip:core/rcu] security: Apply lockdep-based checking to rcu_dereference() uses
    Commit-ID:  e7b0a61b7929632d36cf052d9e2820ef0a9c1bfe
    Gitweb: http://git.kernel.org/tip/e7b0a61b7929632d36cf052d9e2820ef0a9c1bfe
    Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    AuthorDate: Mon, 22 Feb 2010 17:04:56 -0800
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Thu, 25 Feb 2010 10:34:52 +0100

    security: Apply lockdep-based checking to rcu_dereference() uses

    Apply lockdep-ified RCU primitives to key_gc_keyring() and
    keyring_destroy().

    Cc: David Howells <dhowells@redhat.com>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: laijs@cn.fujitsu.com
    Cc: dipankar@in.ibm.com
    Cc: mathieu.desnoyers@polymtl.ca
    Cc: josh@joshtriplett.org
    Cc: dvhltc@us.ibm.com
    Cc: niv@us.ibm.com
    Cc: peterz@infradead.org
    Cc: rostedt@goodmis.org
    Cc: Valdis.Kletnieks@vt.edu
    Cc: dhowells@redhat.com
    LKML-Reference: <1266887105-1528-12-git-send-email-paulmck@linux.vnet.ibm.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    security/keys/gc.c | 3 ++-
    security/keys/keyring.c | 4 +++-
    2 files changed, 5 insertions(+), 2 deletions(-)

    diff --git a/security/keys/gc.c b/security/keys/gc.c
    index 4770be3..1990231 100644
    --- a/security/keys/gc.c
    +++ b/security/keys/gc.c
    @@ -77,7 +77,8 @@ static bool key_gc_keyring(struct key *keyring, time_t limit)
    goto dont_gc;

    /* scan the keyring looking for dead keys */
    - klist = rcu_dereference(keyring->payload.subscriptions);
    + klist = rcu_dereference_check(keyring->payload.subscriptions,
    + lockdep_is_held(&key_serial_lock));
    if (!klist)
    goto dont_gc;

    diff --git a/security/keys/keyring.c b/security/keys/keyring.c
    index 8ec0274..e814d21 100644
    --- a/security/keys/keyring.c
    +++ b/security/keys/keyring.c
    @@ -151,7 +151,9 @@ static void keyring_destroy(struct key *keyring)
    write_unlock(&keyring_name_lock);
    }

    - klist = rcu_dereference(keyring->payload.subscriptions);
    + klist = rcu_dereference_check(keyring->payload.subscriptions,
    + rcu_read_lock_held() ||
    + atomic_read(&keyring->usage) == 0);
    if (klist) {
    for (loop = klist->nkeys - 1; loop >= 0; loop--)
    key_put(klist->keys[loop]);

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