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ipc: move locking out of ipcctl_pre_down_nolock

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This function currently acquires both the rw_mutex and the rcu lock on
successful lookups, leaving the callers to explicitly unlock them,
creating another two level locking situation.

Make the callers (including those that still use ipcctl_pre_down())
explicitly lock and unlock the rwsem and rcu lock.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso
2013-07-08 16:01:12 -07:00
committed by Linus Torvalds
parent cf9d5d78d0
commit 7b4cc5d841
4 changed files with 56 additions and 39 deletions
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27
ipc/sem.c
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@@ -1289,39 +1289,44 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
return -EFAULT;
}
down_write(&sem_ids(ns).rw_mutex);
rcu_read_lock();
ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
&semid64.sem_perm, 0);
if (IS_ERR(ipcp))
return PTR_ERR(ipcp);
if (IS_ERR(ipcp)) {
err = PTR_ERR(ipcp);
/* the ipc lock is not held upon failure */
goto out_unlock1;
}
sma = container_of(ipcp, struct sem_array, sem_perm);
err = security_sem_semctl(sma, cmd);
if (err) {
rcu_read_unlock();
goto out_up;
}
if (err)
goto out_unlock1;
switch(cmd){
switch (cmd) {
case IPC_RMID:
sem_lock(sma, NULL, -1);
/* freeary unlocks the ipc object and rcu */
freeary(ns, ipcp);
goto out_up;
case IPC_SET:
sem_lock(sma, NULL, -1);
err = ipc_update_perm(&semid64.sem_perm, ipcp);
if (err)
goto out_unlock;
goto out_unlock0;
sma->sem_ctime = get_seconds();
break;
default:
rcu_read_unlock();
err = -EINVAL;
goto out_up;
goto out_unlock1;
}
out_unlock:
out_unlock0:
sem_unlock(sma, -1);
out_unlock1:
rcu_read_unlock();
out_up:
up_write(&sem_ids(ns).rw_mutex);