Commit a0d092fc authored by Pierre Peiffer's avatar Pierre Peiffer Committed by Linus Torvalds
Browse files

IPC/message queues: introduce msgctl_down 



Currently, sys_msgctl is not easy to read.

This patch tries to improve that by introducing the msgctl_down function to
handle all commands requiring the rwmutex to be taken in write mode (ie
IPC_SET and IPC_RMID for now).  It is the equivalent function of semctl_down
for message queues.

This greatly changes the readability of sys_msgctl and also harmonizes the way
these commands are handled among all IPCs.

Signed-off-by: default avatarPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8d4cc8b5

ipc/msg.c

+89 −73
Original line number Diff line number Diff line
@@ -436,10 +436,95 @@ copy_msqid_from_user(struct msq_setbuf *out, void __user *buf, int version) 
	}

}



asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)

/*

 * This function handles some msgctl commands which require the rw_mutex

 * to be held in write mode.

 * NOTE: no locks must be held, the rw_mutex is taken inside this function.

 */

static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,

		       struct msqid_ds __user *buf, int version)

{

	struct kern_ipc_perm *ipcp;

	struct msq_setbuf uninitialized_var(setbuf);

	struct msq_setbuf setbuf;

	struct msg_queue *msq;

	int err;



	if (cmd == IPC_SET) {

		if (copy_msqid_from_user(&setbuf, buf, version))

			return -EFAULT;

	}



	down_write(&msg_ids(ns).rw_mutex);

	msq = msg_lock_check_down(ns, msqid);

	if (IS_ERR(msq)) {

		err = PTR_ERR(msq);

		goto out_up;

	}



	ipcp = &msq->q_perm;



	err = audit_ipc_obj(ipcp);

	if (err)

		goto out_unlock;



	if (cmd == IPC_SET) {

		err = audit_ipc_set_perm(setbuf.qbytes, setbuf.uid, setbuf.gid,

					 setbuf.mode);

		if (err)

			goto out_unlock;

	}



	if (current->euid != ipcp->cuid &&

	    current->euid != ipcp->uid &&

	    !capable(CAP_SYS_ADMIN)) {

		/* We _could_ check for CAP_CHOWN above, but we don't */

		err = -EPERM;

		goto out_unlock;

	}



	err = security_msg_queue_msgctl(msq, cmd);

	if (err)

		goto out_unlock;



	switch (cmd) {

	case IPC_RMID:

		freeque(ns, ipcp);

		goto out_up;

	case IPC_SET:

		if (setbuf.qbytes > ns->msg_ctlmnb &&

		    !capable(CAP_SYS_RESOURCE)) {

			err = -EPERM;

			goto out_unlock;

		}



		msq->q_qbytes = setbuf.qbytes;



		ipcp->uid = setbuf.uid;

		ipcp->gid = setbuf.gid;

		ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |

			     (S_IRWXUGO & setbuf.mode);

		msq->q_ctime = get_seconds();

		/* sleeping receivers might be excluded by

		 * stricter permissions.

		 */

		expunge_all(msq, -EAGAIN);

		/* sleeping senders might be able to send

		 * due to a larger queue size.

		 */

		ss_wakeup(&msq->q_senders, 0);

		break;

	default:

		err = -EINVAL;

	}

out_unlock:

	msg_unlock(msq);

out_up:

	up_write(&msg_ids(ns).rw_mutex);

	return err;

}



asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)

{

	struct msg_queue *msq;

	int err, version;

	struct ipc_namespace *ns;
@@ -535,82 +620,13 @@ asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf) 
		return success_return;

	}

	case IPC_SET:

		if (!buf)

			return -EFAULT;

		if (copy_msqid_from_user(&setbuf, buf, version))

			return -EFAULT;

		break;

	case IPC_RMID:

		break;

		err = msgctl_down(ns, msqid, cmd, buf, version);

		return err;

	default:

		return  -EINVAL;

	}



	down_write(&msg_ids(ns).rw_mutex);

	msq = msg_lock_check_down(ns, msqid);

	if (IS_ERR(msq)) {

		err = PTR_ERR(msq);

		goto out_up;

	}



	ipcp = &msq->q_perm;



	err = audit_ipc_obj(ipcp);

	if (err)

		goto out_unlock_up;

	if (cmd == IPC_SET) {

		err = audit_ipc_set_perm(setbuf.qbytes, setbuf.uid, setbuf.gid,

					 setbuf.mode);

		if (err)

			goto out_unlock_up;

	}



	err = -EPERM;

	if (current->euid != ipcp->cuid &&

	    current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN))

		/* We _could_ check for CAP_CHOWN above, but we don't */

		goto out_unlock_up;



	err = security_msg_queue_msgctl(msq, cmd);

	if (err)

		goto out_unlock_up;



	switch (cmd) {

	case IPC_SET:

	{

		err = -EPERM;

		if (setbuf.qbytes > ns->msg_ctlmnb && !capable(CAP_SYS_RESOURCE))

			goto out_unlock_up;



		msq->q_qbytes = setbuf.qbytes;



		ipcp->uid = setbuf.uid;

		ipcp->gid = setbuf.gid;

		ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |

			     (S_IRWXUGO & setbuf.mode);

		msq->q_ctime = get_seconds();

		/* sleeping receivers might be excluded by

		 * stricter permissions.

		 */

		expunge_all(msq, -EAGAIN);

		/* sleeping senders might be able to send

		 * due to a larger queue size.

		 */

		ss_wakeup(&msq->q_senders, 0);

		msg_unlock(msq);

		break;

	}

	case IPC_RMID:

		freeque(ns, &msq->q_perm);

		break;

	}

	err = 0;

out_up:

	up_write(&msg_ids(ns).rw_mutex);

	return err;

out_unlock_up:

	msg_unlock(msq);

	goto out_up;

out_unlock:

	msg_unlock(msq);

	return err;

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