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authorDavidlohr Bueso <davidlohr.bueso@hp.com>2013-07-08 16:01:12 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-10-18 07:45:46 -0700
commitac9bc6e396285ab732dd869c3edb353662134022 (patch)
tree182b0be2e0238d96e02c8669e372c254d6ea81a1 /ipc/msg.c
parent115d40dbef93b70e6f32732b0fdd5903c1f7fce4 (diff)
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ipc: move locking out of ipcctl_pre_down_nolock
commit 7b4cc5d8411bd4e9d61d8714f53859740cf830c2 upstream. 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> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'ipc/msg.c')
-rw-r--r--ipc/msg.c24
1 files changed, 17 insertions, 7 deletions
diff --git a/ipc/msg.c b/ipc/msg.c
index 56bff33457b..6c1609d572c 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -407,31 +407,38 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
return -EFAULT;
}
+ down_write(&msg_ids(ns).rw_mutex);
+ rcu_read_lock();
+
ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
&msqid64.msg_perm, msqid64.msg_qbytes);
- 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;
+ }
msq = container_of(ipcp, struct msg_queue, q_perm);
err = security_msg_queue_msgctl(msq, cmd);
if (err)
- goto out_unlock;
+ goto out_unlock0;
switch (cmd) {
case IPC_RMID:
+ /* freeque unlocks the ipc object and rcu */
freeque(ns, ipcp);
goto out_up;
case IPC_SET:
if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
!capable(CAP_SYS_RESOURCE)) {
err = -EPERM;
- goto out_unlock;
+ goto out_unlock0;
}
err = ipc_update_perm(&msqid64.msg_perm, ipcp);
if (err)
- goto out_unlock;
+ goto out_unlock0;
msq->q_qbytes = msqid64.msg_qbytes;
@@ -448,8 +455,11 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
default:
err = -EINVAL;
}
-out_unlock:
- msg_unlock(msq);
+
+out_unlock0:
+ ipc_unlock_object(&msq->q_perm);
+out_unlock1:
+ rcu_read_unlock();
out_up:
up_write(&msg_ids(ns).rw_mutex);
return err;