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authorDavidlohr Bueso <davidlohr.bueso@hp.com>2013-07-09 03:01:16 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-09 21:33:27 +0400
commitac0ba20ea6f2201a1589d6dc26ad1a4f0f967bb8 (patch)
treebc3e2e4c4140f07ee1861b724ba7e1b295d7bbc6 /ipc/msg.c
parenta5001a0d9768568de5d613c3b3a5b9c7721299da (diff)
downloadlinux-ac0ba20ea6f2201a1589d6dc26ad1a4f0f967bb8.tar.xz
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>
Diffstat (limited to 'ipc/msg.c')
-rw-r--r--ipc/msg.c27
1 files changed, 17 insertions, 10 deletions
diff --git a/ipc/msg.c b/ipc/msg.c
index c53c13716064..c218328b5980 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -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;
}