This is a note to let you know that I've just added the patch titled
ipc,msg: make msgctl_nolock lockless
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipc-msg-make-msgctl_nolock-lockless.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ac0ba20ea6f2201a1589d6dc26ad1a4f0f967bb8 Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Date: Mon, 8 Jul 2013 16:01:16 -0700
Subject: ipc,msg: make msgctl_nolock lockless
From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
commit ac0ba20ea6f2201a1589d6dc26ad1a4f0f967bb8 upstream.
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@xxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
ipc/msg.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -545,17 +545,25 @@ static int msgctl_nolock(struct ipc_name
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_name
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_name
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_name
return err;
out_unlock:
- msg_unlock(msq);
+ rcu_read_unlock();
return err;
}
Patches currently in stable-queue which might be from davidlohr.bueso@xxxxxx are
queue-3.10/ipc-msg-introduce-lockless-functions-to-obtain-the-ipc-object.patch
queue-3.10/ipc-msg-shorten-critical-region-in-msgctl_down.patch
queue-3.10/ipc-remove-unused-functions.patch
queue-3.10/ipc-msg-introduce-msgctl_nolock.patch
queue-3.10/ipc-move-rcu-lock-out-of-ipc_addid.patch
queue-3.10/ipc-msg-shorten-critical-region-in-msgsnd.patch
queue-3.10/ipc-introduce-ipc-object-locking-helpers.patch
queue-3.10/ipc-msg-shorten-critical-region-in-msgrcv.patch
queue-3.10/ipc-msg-make-msgctl_nolock-lockless.patch
queue-3.10/ipc-move-locking-out-of-ipcctl_pre_down_nolock.patch
queue-3.10/ipc-close-open-coded-spin-lock-calls.patch
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