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ipc,msg: make msgctl_nolock lockless 

While the INFO cmd doesn't take the ipc lock, the STAT commands do
acquire it unnecessarily.  We can do the permissions and security checks
only holding the rcu lock.

This function now mimics semctl_nolock().

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 16:01:16 -07:00 committed by Linus Torvalds
parent a5001a0d97
commit ac0ba20ea6
1 changed files with 17 additions and 10 deletions
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27
ipc/msg.c
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@ -545,17 +545,25 @@ static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
if (!buf)
return -EFAULT;
memset(&tbuf, 0, sizeof(tbuf));
rcu_read_lock();
if (cmd == MSG_STAT) {
msq = msg_lock(ns, msqid);
if (IS_ERR(msq))
return PTR_ERR(msq);
msq = msq_obtain_object(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_unlock;
}
success_return = msq->q_perm.id;
} else {
msq = msg_lock_check(ns, msqid);
if (IS_ERR(msq))
return PTR_ERR(msq);
msq = msq_obtain_object_check(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_unlock;
}
success_return = 0;
}
err = -EACCES;
if (ipcperms(ns, &msq->q_perm, S_IRUGO))
goto out_unlock;
@ -564,8 +572,6 @@ static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
if (err)
goto out_unlock;
memset(&tbuf, 0, sizeof(tbuf));
kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
tbuf.msg_stime = msq->q_stime;
tbuf.msg_rtime = msq->q_rtime;
@ -575,7 +581,8 @@ static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
tbuf.msg_qbytes = msq->q_qbytes;
tbuf.msg_lspid = msq->q_lspid;
tbuf.msg_lrpid = msq->q_lrpid;
msg_unlock(msq);
rcu_read_unlock();
if (copy_msqid_to_user(buf, &tbuf, version))
return -EFAULT;
return success_return;
@ -587,7 +594,7 @@ static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
return err;
out_unlock:
msg_unlock(msq);
rcu_read_unlock();
return err;
}