Messages in this thread Patch in this message | | | Date | Fri, 21 Nov 2014 14:52:26 -0500 | From | Rik van Riel <> | Subject | [PATCH] ipc,sem block sem_lock on sma->lock during sma initialization |
| |
When manipulating just one semaphore with semop, sem_lock only takes that single semaphore's lock. This creates a problem during initialization of the semaphore array, when the data structures used by sem_lock have not been set up yet. The sma->lock is already held by newary, and we just have to make sure everything else waits on that lock during initialization.
Luckily it is easy to make sem_lock wait on the sma->lock, by pretending there is a complex operation in progress while the sma is being initialized.
The newary function already zeroes sma->complex_count before unlocking the sma->lock.
Signed-off-by: Rik van Riel <riel@redhat.com> --- ipc/sem.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/ipc/sem.c b/ipc/sem.c index 454f6c6..1823160 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -507,6 +507,9 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params) return retval; } + /* Ensures sem_lock waits on &sma->lock until sma is ready. */ + sma->complex_count = 1; + id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); if (id < 0) { ipc_rcu_putref(sma, sem_rcu_free);
| |