forked from mirrors/linux
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: Pierre Peiffer <pierre.peiffer@bull.net> Acked-by: Serge Hallyn <serue@us.ibm.com> Cc: Nadia Derbey <Nadia.Derbey@bull.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pierre Peiffer
Linus Torvalds
parent
8d4cc8b5c5
commit
a0d092fc2d
1 changed files with 89 additions and 73 deletions
162
ipc/msg.c
162
ipc/msg.c
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@ -436,10 +436,95 @@ copy_msqid_from_user(struct msq_setbuf *out, void __user *buf, int version)
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}
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}
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asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
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/*
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* This function handles some msgctl commands which require the rw_mutex
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* to be held in write mode.
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* NOTE: no locks must be held, the rw_mutex is taken inside this function.
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*/
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static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
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struct msqid_ds __user *buf, int version)
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{
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struct kern_ipc_perm *ipcp;
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struct msq_setbuf uninitialized_var(setbuf);
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struct msq_setbuf setbuf;
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struct msg_queue *msq;
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int err;
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if (cmd == IPC_SET) {
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if (copy_msqid_from_user(&setbuf, buf, version))
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return -EFAULT;
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}
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down_write(&msg_ids(ns).rw_mutex);
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msq = msg_lock_check_down(ns, msqid);
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if (IS_ERR(msq)) {
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err = PTR_ERR(msq);
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goto out_up;
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}
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ipcp = &msq->q_perm;
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err = audit_ipc_obj(ipcp);
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if (err)
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goto out_unlock;
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if (cmd == IPC_SET) {
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err = audit_ipc_set_perm(setbuf.qbytes, setbuf.uid, setbuf.gid,
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setbuf.mode);
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if (err)
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goto out_unlock;
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}
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if (current->euid != ipcp->cuid &&
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current->euid != ipcp->uid &&
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!capable(CAP_SYS_ADMIN)) {
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/* We _could_ check for CAP_CHOWN above, but we don't */
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err = -EPERM;
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goto out_unlock;
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}
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err = security_msg_queue_msgctl(msq, cmd);
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if (err)
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goto out_unlock;
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switch (cmd) {
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case IPC_RMID:
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freeque(ns, ipcp);
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goto out_up;
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case IPC_SET:
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if (setbuf.qbytes > ns->msg_ctlmnb &&
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!capable(CAP_SYS_RESOURCE)) {
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err = -EPERM;
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goto out_unlock;
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}
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msq->q_qbytes = setbuf.qbytes;
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ipcp->uid = setbuf.uid;
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ipcp->gid = setbuf.gid;
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ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |
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(S_IRWXUGO & setbuf.mode);
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msq->q_ctime = get_seconds();
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/* sleeping receivers might be excluded by
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* stricter permissions.
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*/
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expunge_all(msq, -EAGAIN);
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/* sleeping senders might be able to send
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* due to a larger queue size.
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*/
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ss_wakeup(&msq->q_senders, 0);
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break;
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default:
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err = -EINVAL;
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}
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out_unlock:
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msg_unlock(msq);
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out_up:
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up_write(&msg_ids(ns).rw_mutex);
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return err;
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}
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asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
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{
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struct msg_queue *msq;
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int err, version;
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struct ipc_namespace *ns;
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@ -535,82 +620,13 @@ asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
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return success_return;
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}
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case IPC_SET:
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if (!buf)
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return -EFAULT;
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if (copy_msqid_from_user(&setbuf, buf, version))
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return -EFAULT;
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break;
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case IPC_RMID:
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break;
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err = msgctl_down(ns, msqid, cmd, buf, version);
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return err;
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default:
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return -EINVAL;
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}
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down_write(&msg_ids(ns).rw_mutex);
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msq = msg_lock_check_down(ns, msqid);
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if (IS_ERR(msq)) {
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err = PTR_ERR(msq);
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goto out_up;
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}
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ipcp = &msq->q_perm;
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err = audit_ipc_obj(ipcp);
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if (err)
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goto out_unlock_up;
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if (cmd == IPC_SET) {
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err = audit_ipc_set_perm(setbuf.qbytes, setbuf.uid, setbuf.gid,
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setbuf.mode);
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if (err)
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goto out_unlock_up;
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}
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err = -EPERM;
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if (current->euid != ipcp->cuid &&
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current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN))
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/* We _could_ check for CAP_CHOWN above, but we don't */
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goto out_unlock_up;
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err = security_msg_queue_msgctl(msq, cmd);
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if (err)
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goto out_unlock_up;
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switch (cmd) {
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case IPC_SET:
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{
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err = -EPERM;
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if (setbuf.qbytes > ns->msg_ctlmnb && !capable(CAP_SYS_RESOURCE))
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goto out_unlock_up;
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msq->q_qbytes = setbuf.qbytes;
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ipcp->uid = setbuf.uid;
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ipcp->gid = setbuf.gid;
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ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |
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(S_IRWXUGO & setbuf.mode);
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msq->q_ctime = get_seconds();
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/* sleeping receivers might be excluded by
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* stricter permissions.
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*/
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expunge_all(msq, -EAGAIN);
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/* sleeping senders might be able to send
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* due to a larger queue size.
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*/
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ss_wakeup(&msq->q_senders, 0);
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msg_unlock(msq);
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break;
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}
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case IPC_RMID:
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freeque(ns, &msq->q_perm);
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break;
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}
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err = 0;
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out_up:
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up_write(&msg_ids(ns).rw_mutex);
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return err;
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out_unlock_up:
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msg_unlock(msq);
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goto out_up;
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out_unlock:
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msg_unlock(msq);
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return err;
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