ipc: move locking out of ipcctl_pre_down_nolock
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:

committed by
Linus Torvalds

parent
cf9d5d78d0
commit
7b4cc5d841
24
ipc/msg.c
24
ipc/msg.c
@@ -407,31 +407,38 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
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return -EFAULT;
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}
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down_write(&msg_ids(ns).rw_mutex);
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rcu_read_lock();
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ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
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&msqid64.msg_perm, msqid64.msg_qbytes);
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if (IS_ERR(ipcp))
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return PTR_ERR(ipcp);
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if (IS_ERR(ipcp)) {
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err = PTR_ERR(ipcp);
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/* the ipc lock is not held upon failure */
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goto out_unlock1;
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}
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msq = container_of(ipcp, struct msg_queue, q_perm);
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err = security_msg_queue_msgctl(msq, cmd);
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if (err)
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goto out_unlock;
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goto out_unlock0;
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switch (cmd) {
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case IPC_RMID:
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/* freeque unlocks the ipc object and rcu */
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freeque(ns, ipcp);
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goto out_up;
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case IPC_SET:
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if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
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!capable(CAP_SYS_RESOURCE)) {
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err = -EPERM;
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goto out_unlock;
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goto out_unlock0;
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}
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err = ipc_update_perm(&msqid64.msg_perm, ipcp);
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if (err)
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goto out_unlock;
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goto out_unlock0;
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msq->q_qbytes = msqid64.msg_qbytes;
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@@ -448,8 +455,11 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
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default:
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err = -EINVAL;
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}
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out_unlock:
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msg_unlock(msq);
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out_unlock0:
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ipc_unlock_object(&msq->q_perm);
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out_unlock1:
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rcu_read_unlock();
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out_up:
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up_write(&msg_ids(ns).rw_mutex);
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return err;
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