diff options
Diffstat (limited to 'ipc/msg.c')
| -rw-r--r-- | ipc/msg.c | 1046 |
1 files changed, 1046 insertions, 0 deletions
diff --git a/ipc/msg.c b/ipc/msg.c new file mode 100644 index 000000000..2b6fdbb9e --- /dev/null +++ b/ipc/msg.c @@ -0,0 +1,1046 @@ +/* + * linux/ipc/msg.c + * Copyright (C) 1992 Krishna Balasubramanian + * + * Removed all the remaining kerneld mess + * Catch the -EFAULT stuff properly + * Use GFP_KERNEL for messages as in 1.2 + * Fixed up the unchecked user space derefs + * Copyright (C) 1998 Alan Cox & Andi Kleen + * + * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com> + * + * mostly rewritten, threaded and wake-one semantics added + * MSGMAX limit removed, sysctl's added + * (c) 1999 Manfred Spraul <manfred@colorfullife.com> + * + * support for audit of ipc object properties and permission changes + * Dustin Kirkland <dustin.kirkland@us.ibm.com> + * + * namespaces support + * OpenVZ, SWsoft Inc. + * Pavel Emelianov <xemul@openvz.org> + */ + +#include <linux/capability.h> +#include <linux/msg.h> +#include <linux/spinlock.h> +#include <linux/init.h> +#include <linux/mm.h> +#include <linux/proc_fs.h> +#include <linux/list.h> +#include <linux/security.h> +#include <linux/sched.h> +#include <linux/syscalls.h> +#include <linux/audit.h> +#include <linux/seq_file.h> +#include <linux/rwsem.h> +#include <linux/nsproxy.h> +#include <linux/ipc_namespace.h> + +#include <asm/current.h> +#include <linux/uaccess.h> +#include "util.h" + +/* one msg_receiver structure for each sleeping receiver */ +struct msg_receiver { + struct list_head r_list; + struct task_struct *r_tsk; + + int r_mode; + long r_msgtype; + long r_maxsize; + + /* + * Mark r_msg volatile so that the compiler + * does not try to get smart and optimize + * it. We rely on this for the lockless + * receive algorithm. + */ + struct msg_msg *volatile r_msg; +}; + +/* one msg_sender for each sleeping sender */ +struct msg_sender { + struct list_head list; + struct task_struct *tsk; +}; + +#define SEARCH_ANY 1 +#define SEARCH_EQUAL 2 +#define SEARCH_NOTEQUAL 3 +#define SEARCH_LESSEQUAL 4 +#define SEARCH_NUMBER 5 + +#define msg_ids(ns) ((ns)->ids[IPC_MSG_IDS]) + +static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id) +{ + struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id); + + if (IS_ERR(ipcp)) + return ERR_CAST(ipcp); + + return container_of(ipcp, struct msg_queue, q_perm); +} + +static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns, + int id) +{ + struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id); + + if (IS_ERR(ipcp)) + return ERR_CAST(ipcp); + + return container_of(ipcp, struct msg_queue, q_perm); +} + +static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s) +{ + ipc_rmid(&msg_ids(ns), &s->q_perm); +} + +static void msg_rcu_free(struct rcu_head *head) +{ + struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu); + struct msg_queue *msq = ipc_rcu_to_struct(p); + + security_msg_queue_free(msq); + ipc_rcu_free(head); +} + +/** + * newque - Create a new msg queue + * @ns: namespace + * @params: ptr to the structure that contains the key and msgflg + * + * Called with msg_ids.rwsem held (writer) + */ +static int newque(struct ipc_namespace *ns, struct ipc_params *params) +{ + struct msg_queue *msq; + int id, retval; + key_t key = params->key; + int msgflg = params->flg; + + msq = ipc_rcu_alloc(sizeof(*msq)); + if (!msq) + return -ENOMEM; + + msq->q_perm.mode = msgflg & S_IRWXUGO; + msq->q_perm.key = key; + + msq->q_perm.security = NULL; + retval = security_msg_queue_alloc(msq); + if (retval) { + ipc_rcu_putref(msq, ipc_rcu_free); + return retval; + } + + /* ipc_addid() locks msq upon success. */ + id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni); + if (id < 0) { + ipc_rcu_putref(msq, msg_rcu_free); + return id; + } + + msq->q_stime = msq->q_rtime = 0; + msq->q_ctime = get_seconds(); + msq->q_cbytes = msq->q_qnum = 0; + msq->q_qbytes = ns->msg_ctlmnb; + msq->q_lspid = msq->q_lrpid = 0; + INIT_LIST_HEAD(&msq->q_messages); + INIT_LIST_HEAD(&msq->q_receivers); + INIT_LIST_HEAD(&msq->q_senders); + + ipc_unlock_object(&msq->q_perm); + rcu_read_unlock(); + + return msq->q_perm.id; +} + +static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss) +{ + mss->tsk = current; + __set_current_state(TASK_INTERRUPTIBLE); + list_add_tail(&mss->list, &msq->q_senders); +} + +static inline void ss_del(struct msg_sender *mss) +{ + if (mss->list.next != NULL) + list_del(&mss->list); +} + +static void ss_wakeup(struct list_head *h, int kill) +{ + struct msg_sender *mss, *t; + + list_for_each_entry_safe(mss, t, h, list) { + if (kill) + mss->list.next = NULL; + wake_up_process(mss->tsk); + } +} + +static void expunge_all(struct msg_queue *msq, int res) +{ + struct msg_receiver *msr, *t; + + list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) { + msr->r_msg = NULL; /* initialize expunge ordering */ + wake_up_process(msr->r_tsk); + /* + * Ensure that the wakeup is visible before setting r_msg as + * the receiving end depends on it: either spinning on a nil, + * or dealing with -EAGAIN cases. See lockless receive part 1 + * and 2 in do_msgrcv(). + */ + smp_mb(); + msr->r_msg = ERR_PTR(res); + } +} + +/* + * freeque() wakes up waiters on the sender and receiver waiting queue, + * removes the message queue from message queue ID IDR, and cleans up all the + * messages associated with this queue. + * + * msg_ids.rwsem (writer) and the spinlock for this message queue are held + * before freeque() is called. msg_ids.rwsem remains locked on exit. + */ +static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) +{ + struct msg_msg *msg, *t; + struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm); + + expunge_all(msq, -EIDRM); + ss_wakeup(&msq->q_senders, 1); + msg_rmid(ns, msq); + ipc_unlock_object(&msq->q_perm); + rcu_read_unlock(); + + list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) { + atomic_dec(&ns->msg_hdrs); + free_msg(msg); + } + atomic_sub(msq->q_cbytes, &ns->msg_bytes); + ipc_rcu_putref(msq, msg_rcu_free); +} + +/* + * Called with msg_ids.rwsem and ipcp locked. + */ +static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg) +{ + struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm); + + return security_msg_queue_associate(msq, msgflg); +} + +SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg) +{ + struct ipc_namespace *ns; + static const struct ipc_ops msg_ops = { + .getnew = newque, + .associate = msg_security, + }; + struct ipc_params msg_params; + + ns = current->nsproxy->ipc_ns; + + msg_params.key = key; + msg_params.flg = msgflg; + + return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params); +} + +static inline unsigned long +copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version) +{ + switch (version) { + case IPC_64: + return copy_to_user(buf, in, sizeof(*in)); + case IPC_OLD: + { + struct msqid_ds out; + + memset(&out, 0, sizeof(out)); + + ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm); + + out.msg_stime = in->msg_stime; + out.msg_rtime = in->msg_rtime; + out.msg_ctime = in->msg_ctime; + + if (in->msg_cbytes > USHRT_MAX) + out.msg_cbytes = USHRT_MAX; + else + out.msg_cbytes = in->msg_cbytes; + out.msg_lcbytes = in->msg_cbytes; + + if (in->msg_qnum > USHRT_MAX) + out.msg_qnum = USHRT_MAX; + else + out.msg_qnum = in->msg_qnum; + + if (in->msg_qbytes > USHRT_MAX) + out.msg_qbytes = USHRT_MAX; + else + out.msg_qbytes = in->msg_qbytes; + out.msg_lqbytes = in->msg_qbytes; + + out.msg_lspid = in->msg_lspid; + out.msg_lrpid = in->msg_lrpid; + + return copy_to_user(buf, &out, sizeof(out)); + } + default: + return -EINVAL; + } +} + +static inline unsigned long +copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version) +{ + switch (version) { + case IPC_64: + if (copy_from_user(out, buf, sizeof(*out))) + return -EFAULT; + return 0; + case IPC_OLD: + { + struct msqid_ds tbuf_old; + + if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) + return -EFAULT; + + out->msg_perm.uid = tbuf_old.msg_perm.uid; + out->msg_perm.gid = tbuf_old.msg_perm.gid; + out->msg_perm.mode = tbuf_old.msg_perm.mode; + + if (tbuf_old.msg_qbytes == 0) + out->msg_qbytes = tbuf_old.msg_lqbytes; + else + out->msg_qbytes = tbuf_old.msg_qbytes; + + return 0; + } + default: + return -EINVAL; + } +} + +/* + * This function handles some msgctl commands which require the rwsem + * to be held in write mode. + * NOTE: no locks must be held, the rwsem 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 msqid64_ds uninitialized_var(msqid64); + struct msg_queue *msq; + int err; + + if (cmd == IPC_SET) { + if (copy_msqid_from_user(&msqid64, buf, version)) + return -EFAULT; + } + + down_write(&msg_ids(ns).rwsem); + rcu_read_lock(); + + 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); + goto out_unlock1; + } + + msq = container_of(ipcp, struct msg_queue, q_perm); + + err = security_msg_queue_msgctl(msq, cmd); + if (err) + 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; + case IPC_SET: + if (msqid64.msg_qbytes > ns->msg_ctlmnb && + !capable(CAP_SYS_RESOURCE)) { + err = -EPERM; + goto out_unlock1; + } + + ipc_lock_object(&msq->q_perm); + err = ipc_update_perm(&msqid64.msg_perm, ipcp); + if (err) + goto out_unlock0; + + msq->q_qbytes = msqid64.msg_qbytes; + + 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; + goto out_unlock1; + } + +out_unlock0: + ipc_unlock_object(&msq->q_perm); +out_unlock1: + rcu_read_unlock(); +out_up: + up_write(&msg_ids(ns).rwsem); + return err; +} + +static int msgctl_nolock(struct ipc_namespace *ns, int msqid, + int cmd, int version, void __user *buf) +{ + int err; + struct msg_queue *msq; + + switch (cmd) { + case IPC_INFO: + case MSG_INFO: + { + struct msginfo msginfo; + int max_id; + + if (!buf) + return -EFAULT; + + /* + * We must not return kernel stack data. + * due to padding, it's not enough + * to set all member fields. + */ + err = security_msg_queue_msgctl(NULL, cmd); + if (err) + return err; + + memset(&msginfo, 0, sizeof(msginfo)); + msginfo.msgmni = ns->msg_ctlmni; + msginfo.msgmax = ns->msg_ctlmax; + msginfo.msgmnb = ns->msg_ctlmnb; + msginfo.msgssz = MSGSSZ; + msginfo.msgseg = MSGSEG; + down_read(&msg_ids(ns).rwsem); + if (cmd == MSG_INFO) { + msginfo.msgpool = msg_ids(ns).in_use; + msginfo.msgmap = atomic_read(&ns->msg_hdrs); + msginfo.msgtql = atomic_read(&ns->msg_bytes); + } else { + msginfo.msgmap = MSGMAP; + msginfo.msgpool = MSGPOOL; + msginfo.msgtql = MSGTQL; + } + max_id = ipc_get_maxid(&msg_ids(ns)); + up_read(&msg_ids(ns).rwsem); + if (copy_to_user(buf, &msginfo, sizeof(struct msginfo))) + return -EFAULT; + return (max_id < 0) ? 0 : max_id; + } + + case MSG_STAT: + case IPC_STAT: + { + struct msqid64_ds tbuf; + int success_return; + + if (!buf) + return -EFAULT; + + memset(&tbuf, 0, sizeof(tbuf)); + + rcu_read_lock(); + if (cmd == MSG_STAT) { + 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 = 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; + + err = security_msg_queue_msgctl(msq, cmd); + if (err) + goto out_unlock; + + kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm); + tbuf.msg_stime = msq->q_stime; + tbuf.msg_rtime = msq->q_rtime; + tbuf.msg_ctime = msq->q_ctime; + tbuf.msg_cbytes = msq->q_cbytes; + tbuf.msg_qnum = msq->q_qnum; + tbuf.msg_qbytes = msq->q_qbytes; + tbuf.msg_lspid = msq->q_lspid; + tbuf.msg_lrpid = msq->q_lrpid; + rcu_read_unlock(); + + if (copy_msqid_to_user(buf, &tbuf, version)) + return -EFAULT; + return success_return; + } + + default: + return -EINVAL; + } + + return err; +out_unlock: + rcu_read_unlock(); + return err; +} + +SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf) +{ + int version; + struct ipc_namespace *ns; + + if (msqid < 0 || cmd < 0) + return -EINVAL; + + version = ipc_parse_version(&cmd); + ns = current->nsproxy->ipc_ns; + + switch (cmd) { + case IPC_INFO: + case MSG_INFO: + case MSG_STAT: /* msqid is an index rather than a msg queue id */ + case IPC_STAT: + return msgctl_nolock(ns, msqid, cmd, version, buf); + case IPC_SET: + case IPC_RMID: + return msgctl_down(ns, msqid, cmd, buf, version); + default: + return -EINVAL; + } +} + +static int testmsg(struct msg_msg *msg, long type, int mode) +{ + switch (mode) { + case SEARCH_ANY: + case SEARCH_NUMBER: + return 1; + case SEARCH_LESSEQUAL: + if (msg->m_type <= type) + return 1; + break; + case SEARCH_EQUAL: + if (msg->m_type == type) + return 1; + break; + case SEARCH_NOTEQUAL: + if (msg->m_type != type) + return 1; + break; + } + return 0; +} + +static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg) +{ + struct msg_receiver *msr, *t; + + list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) { + if (testmsg(msg, msr->r_msgtype, msr->r_mode) && + !security_msg_queue_msgrcv(msq, msg, msr->r_tsk, + msr->r_msgtype, msr->r_mode)) { + + list_del(&msr->r_list); + if (msr->r_maxsize < msg->m_ts) { + /* initialize pipelined send ordering */ + msr->r_msg = NULL; + wake_up_process(msr->r_tsk); + smp_mb(); /* see barrier comment below */ + msr->r_msg = ERR_PTR(-E2BIG); + } else { + msr->r_msg = NULL; + msq->q_lrpid = task_pid_vnr(msr->r_tsk); + msq->q_rtime = get_seconds(); + wake_up_process(msr->r_tsk); + /* + * Ensure that the wakeup is visible before + * setting r_msg, as the receiving end depends + * on it. See lockless receive part 1 and 2 in + * do_msgrcv(). + */ + smp_mb(); + msr->r_msg = msg; + + return 1; + } + } + } + + return 0; +} + +long do_msgsnd(int msqid, long mtype, void __user *mtext, + size_t msgsz, int msgflg) +{ + struct msg_queue *msq; + struct msg_msg *msg; + int err; + struct ipc_namespace *ns; + + ns = current->nsproxy->ipc_ns; + + if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0) + return -EINVAL; + if (mtype < 1) + return -EINVAL; + + msg = load_msg(mtext, msgsz); + if (IS_ERR(msg)) + return PTR_ERR(msg); + + msg->m_type = mtype; + msg->m_ts = msgsz; + + rcu_read_lock(); + msq = msq_obtain_object_check(ns, msqid); + if (IS_ERR(msq)) { + err = PTR_ERR(msq); + goto out_unlock1; + } + + ipc_lock_object(&msq->q_perm); + + for (;;) { + struct msg_sender s; + + err = -EACCES; + if (ipcperms(ns, &msq->q_perm, S_IWUGO)) + goto out_unlock0; + + /* raced with RMID? */ + if (!ipc_valid_object(&msq->q_perm)) { + err = -EIDRM; + goto out_unlock0; + } + + err = security_msg_queue_msgsnd(msq, msg, msgflg); + if (err) + goto out_unlock0; + + if (msgsz + msq->q_cbytes <= msq->q_qbytes && + 1 + msq->q_qnum <= msq->q_qbytes) { + break; + } + + /* queue full, wait: */ + if (msgflg & IPC_NOWAIT) { + err = -EAGAIN; + goto out_unlock0; + } + + /* enqueue the sender and prepare to block */ + ss_add(msq, &s); + + if (!ipc_rcu_getref(msq)) { + err = -EIDRM; + goto out_unlock0; + } + + ipc_unlock_object(&msq->q_perm); + rcu_read_unlock(); + schedule(); + + rcu_read_lock(); + ipc_lock_object(&msq->q_perm); + + ipc_rcu_putref(msq, ipc_rcu_free); + /* raced with RMID? */ + if (!ipc_valid_object(&msq->q_perm)) { + err = -EIDRM; + goto out_unlock0; + } + + ss_del(&s); + + if (signal_pending(current)) { + err = -ERESTARTNOHAND; + goto out_unlock0; + } + + } + msq->q_lspid = task_tgid_vnr(current); + msq->q_stime = get_seconds(); + + if (!pipelined_send(msq, msg)) { + /* no one is waiting for this message, enqueue it */ + list_add_tail(&msg->m_list, &msq->q_messages); + msq->q_cbytes += msgsz; + msq->q_qnum++; + atomic_add(msgsz, &ns->msg_bytes); + atomic_inc(&ns->msg_hdrs); + } + + err = 0; + msg = NULL; + +out_unlock0: + ipc_unlock_object(&msq->q_perm); +out_unlock1: + rcu_read_unlock(); + if (msg != NULL) + free_msg(msg); + return err; +} + +SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, + int, msgflg) +{ + long mtype; + + if (get_user(mtype, &msgp->mtype)) + return -EFAULT; + return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg); +} + +static inline int convert_mode(long *msgtyp, int msgflg) +{ + if (msgflg & MSG_COPY) + return SEARCH_NUMBER; + /* + * find message of correct type. + * msgtyp = 0 => get first. + * msgtyp > 0 => get first message of matching type. + * msgtyp < 0 => get message with least type must be < abs(msgtype). + */ + if (*msgtyp == 0) + return SEARCH_ANY; + if (*msgtyp < 0) { + *msgtyp = -*msgtyp; + return SEARCH_LESSEQUAL; + } + if (msgflg & MSG_EXCEPT) + return SEARCH_NOTEQUAL; + return SEARCH_EQUAL; +} + +static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz) +{ + struct msgbuf __user *msgp = dest; + size_t msgsz; + + if (put_user(msg->m_type, &msgp->mtype)) + return -EFAULT; + + msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz; + if (store_msg(msgp->mtext, msg, msgsz)) + return -EFAULT; + return msgsz; +} + +#ifdef CONFIG_CHECKPOINT_RESTORE +/* + * This function creates new kernel message structure, large enough to store + * bufsz message bytes. + */ +static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) +{ + struct msg_msg *copy; + + /* + * Create dummy message to copy real message to. + */ + copy = load_msg(buf, bufsz); + if (!IS_ERR(copy)) + copy->m_ts = bufsz; + return copy; +} + +static inline void free_copy(struct msg_msg *copy) +{ + if (copy) + free_msg(copy); +} +#else +static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) +{ + return ERR_PTR(-ENOSYS); +} + +static inline void free_copy(struct msg_msg *copy) +{ +} +#endif + +static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode) +{ + struct msg_msg *msg, *found = NULL; + long count = 0; + + list_for_each_entry(msg, &msq->q_messages, m_list) { + if (testmsg(msg, *msgtyp, mode) && + !security_msg_queue_msgrcv(msq, msg, current, + *msgtyp, mode)) { + if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) { + *msgtyp = msg->m_type - 1; + found = msg; + } else if (mode == SEARCH_NUMBER) { + if (*msgtyp == count) + return msg; + } else + return msg; + count++; + } + } + + return found ?: ERR_PTR(-EAGAIN); +} + +long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg, + long (*msg_handler)(void __user *, struct msg_msg *, size_t)) +{ + int mode; + struct msg_queue *msq; + struct ipc_namespace *ns; + struct msg_msg *msg, *copy = NULL; + + ns = current->nsproxy->ipc_ns; + + if (msqid < 0 || (long) bufsz < 0) + return -EINVAL; + + if (msgflg & MSG_COPY) { + if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT)) + return -EINVAL; + copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax)); + if (IS_ERR(copy)) + return PTR_ERR(copy); + } + mode = convert_mode(&msgtyp, msgflg); + + rcu_read_lock(); + msq = msq_obtain_object_check(ns, msqid); + if (IS_ERR(msq)) { + rcu_read_unlock(); + free_copy(copy); + return PTR_ERR(msq); + } + + for (;;) { + struct msg_receiver msr_d; + + msg = ERR_PTR(-EACCES); + if (ipcperms(ns, &msq->q_perm, S_IRUGO)) + goto out_unlock1; + + ipc_lock_object(&msq->q_perm); + + /* raced with RMID? */ + if (!ipc_valid_object(&msq->q_perm)) { + msg = ERR_PTR(-EIDRM); + goto out_unlock0; + } + + msg = find_msg(msq, &msgtyp, mode); + if (!IS_ERR(msg)) { + /* + * Found a suitable message. + * Unlink it from the queue. + */ + if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) { + msg = ERR_PTR(-E2BIG); + goto out_unlock0; + } + /* + * If we are copying, then do not unlink message and do + * not update queue parameters. + */ + if (msgflg & MSG_COPY) { + msg = copy_msg(msg, copy); + goto out_unlock0; + } + + list_del(&msg->m_list); + msq->q_qnum--; + msq->q_rtime = get_seconds(); + msq->q_lrpid = task_tgid_vnr(current); + msq->q_cbytes -= msg->m_ts; + atomic_sub(msg->m_ts, &ns->msg_bytes); + atomic_dec(&ns->msg_hdrs); + ss_wakeup(&msq->q_senders, 0); + + goto out_unlock0; + } + + /* No message waiting. Wait for a message */ + if (msgflg & IPC_NOWAIT) { + msg = ERR_PTR(-ENOMSG); + goto out_unlock0; + } + + list_add_tail(&msr_d.r_list, &msq->q_receivers); + msr_d.r_tsk = current; + msr_d.r_msgtype = msgtyp; + msr_d.r_mode = mode; + if (msgflg & MSG_NOERROR) + msr_d.r_maxsize = INT_MAX; + else + msr_d.r_maxsize = bufsz; + msr_d.r_msg = ERR_PTR(-EAGAIN); + __set_current_state(TASK_INTERRUPTIBLE); + + ipc_unlock_object(&msq->q_perm); + rcu_read_unlock(); + schedule(); + + /* Lockless receive, part 1: + * Disable preemption. We don't hold a reference to the queue + * and getting a reference would defeat the idea of a lockless + * operation, thus the code relies on rcu to guarantee the + * existence of msq: + * Prior to destruction, expunge_all(-EIRDM) changes r_msg. + * Thus if r_msg is -EAGAIN, then the queue not yet destroyed. + * rcu_read_lock() prevents preemption between reading r_msg + * and acquiring the q_perm.lock in ipc_lock_object(). + */ + rcu_read_lock(); + + /* Lockless receive, part 2: + * Wait until pipelined_send or expunge_all are outside of + * wake_up_process(). There is a race with exit(), see + * ipc/mqueue.c for the details. + */ + msg = (struct msg_msg *)msr_d.r_msg; + while (msg == NULL) { + cpu_relax(); + msg = (struct msg_msg *)msr_d.r_msg; + } + + /* Lockless receive, part 3: + * If there is a message or an error then accept it without + * locking. + */ + if (msg != ERR_PTR(-EAGAIN)) + goto out_unlock1; + + /* Lockless receive, part 3: + * Acquire the queue spinlock. + */ + ipc_lock_object(&msq->q_perm); + + /* Lockless receive, part 4: + * Repeat test after acquiring the spinlock. + */ + msg = (struct msg_msg *)msr_d.r_msg; + if (msg != ERR_PTR(-EAGAIN)) + goto out_unlock0; + + list_del(&msr_d.r_list); + if (signal_pending(current)) { + msg = ERR_PTR(-ERESTARTNOHAND); + goto out_unlock0; + } + + ipc_unlock_object(&msq->q_perm); + } + +out_unlock0: + ipc_unlock_object(&msq->q_perm); +out_unlock1: + rcu_read_unlock(); + if (IS_ERR(msg)) { + free_copy(copy); + return PTR_ERR(msg); + } + + bufsz = msg_handler(buf, msg, bufsz); + free_msg(msg); + + return bufsz; +} + +SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, + long, msgtyp, int, msgflg) +{ + return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill); +} + + +void msg_init_ns(struct ipc_namespace *ns) +{ + ns->msg_ctlmax = MSGMAX; + ns->msg_ctlmnb = MSGMNB; + ns->msg_ctlmni = MSGMNI; + + atomic_set(&ns->msg_bytes, 0); + atomic_set(&ns->msg_hdrs, 0); + ipc_init_ids(&ns->ids[IPC_MSG_IDS]); +} + +#ifdef CONFIG_IPC_NS +void msg_exit_ns(struct ipc_namespace *ns) +{ + free_ipcs(ns, &msg_ids(ns), freeque); + idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr); +} +#endif + +#ifdef CONFIG_PROC_FS +static int sysvipc_msg_proc_show(struct seq_file *s, void *it) +{ + struct user_namespace *user_ns = seq_user_ns(s); + struct msg_queue *msq = it; + + seq_printf(s, + "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n", + msq->q_perm.key, + msq->q_perm.id, + msq->q_perm.mode, + msq->q_cbytes, + msq->q_qnum, + msq->q_lspid, + msq->q_lrpid, + from_kuid_munged(user_ns, msq->q_perm.uid), + from_kgid_munged(user_ns, msq->q_perm.gid), + from_kuid_munged(user_ns, msq->q_perm.cuid), + from_kgid_munged(user_ns, msq->q_perm.cgid), + msq->q_stime, + msq->q_rtime, + msq->q_ctime); + + return 0; +} +#endif + +void __init msg_init(void) +{ + msg_init_ns(&init_ipc_ns); + + ipc_init_proc_interface("sysvipc/msg", + " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n", + IPC_MSG_IDS, sysvipc_msg_proc_show); +} |