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Subject[ 34/69] ipc,msg: shorten critical region in msgctl_down
Date
3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davidlohr Bueso <davidlohr.bueso@hp.com>

commit 15724ecb7e9bab35fc694c666ad563adba820cc3 upstream.

Instead of holding the ipc lock for the entire function, use the
ipcctl_pre_down_nolock and only acquire the lock for specific commands:
RMID and SET.

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>

---
ipc/msg.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -410,11 +410,10 @@ static int msgctl_down(struct ipc_namesp
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);
+ ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
+ &msqid64.msg_perm, msqid64.msg_qbytes);
if (IS_ERR(ipcp)) {
err = PTR_ERR(ipcp);
- /* the ipc lock is not held upon failure */
goto out_unlock1;
}

@@ -422,10 +421,11 @@ static int msgctl_down(struct ipc_namesp

err = security_msg_queue_msgctl(msq, cmd);
if (err)
- goto out_unlock0;
+ goto out_unlock1;

switch (cmd) {
case IPC_RMID:
+ ipc_lock_object(&msq->q_perm);
/* freeque unlocks the ipc object and rcu */
freeque(ns, ipcp);
goto out_up;
@@ -433,9 +433,10 @@ static int msgctl_down(struct ipc_namesp
if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
!capable(CAP_SYS_RESOURCE)) {
err = -EPERM;
- goto out_unlock0;
+ goto out_unlock1;
}

+ ipc_lock_object(&msq->q_perm);
err = ipc_update_perm(&msqid64.msg_perm, ipcp);
if (err)
goto out_unlock0;
@@ -454,6 +455,7 @@ static int msgctl_down(struct ipc_namesp
break;
default:
err = -EINVAL;
+ goto out_unlock1;
}

out_unlock0:



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