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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 <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Rik van Riel <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Davidlohr Bueso 2013-07-08 16:01:12 -07:00 • committed by Linus Torvalds
commit 7b4cc5d841
4 changed files with 56 additions and 39 deletions
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23
ipc/shm.c
View file

@ -757,31 +757,42 @@ static int shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,
return -EFAULT;
}
down_write(&shm_ids(ns).rw_mutex);
rcu_read_lock();
ipcp = ipcctl_pre_down(ns, &shm_ids(ns), shmid, cmd,
&shmid64.shm_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;
}
shp = container_of(ipcp, struct shmid_kernel, shm_perm);
err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock;
goto out_unlock0;
switch (cmd) {
case IPC_RMID:
/* do_shm_rmid unlocks the ipc object and rcu */
do_shm_rmid(ns, ipcp);
goto out_up;
case IPC_SET:
err = ipc_update_perm(&shmid64.shm_perm, ipcp);
if (err)
goto out_unlock;
goto out_unlock0;
shp->shm_ctim = get_seconds();
break;
default:
err = -EINVAL;
}
out_unlock:
shm_unlock(shp);
out_unlock0:
ipc_unlock_object(&shp->shm_perm);
out_unlock1:
rcu_read_unlock();
out_up:
up_write(&shm_ids(ns).rw_mutex);
return err;