diff options
Diffstat (limited to 'ipc/msg.c')
| -rw-r--r-- | ipc/msg.c | 944 |
1 files changed, 944 insertions, 0 deletions
diff --git a/ipc/msg.c b/ipc/msg.c new file mode 100644 index 0000000..2ceab7f --- /dev/null +++ b/ipc/msg.c @@ -0,0 +1,944 @@ +/* + * 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/slab.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 <asm/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; + + 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 msg_ids(ns) ((ns)->ids[IPC_MSG_IDS]) + +#define msg_unlock(msq) ipc_unlock(&(msq)->q_perm) + +static void freeque(struct ipc_namespace *, struct kern_ipc_perm *); +static int newque(struct ipc_namespace *, struct ipc_params *); +#ifdef CONFIG_PROC_FS +static int sysvipc_msg_proc_show(struct seq_file *s, void *it); +#endif + +/* + * Scale msgmni with the available lowmem size: the memory dedicated to msg + * queues should occupy at most 1/MSG_MEM_SCALE of lowmem. + * Also take into account the number of nsproxies created so far. + * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range. + */ +void recompute_msgmni(struct ipc_namespace *ns) +{ + struct sysinfo i; + unsigned long allowed; + int nb_ns; + + si_meminfo(&i); + allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit) + / MSGMNB; + nb_ns = atomic_read(&nr_ipc_ns); + allowed /= nb_ns; + + if (allowed < MSGMNI) { + ns->msg_ctlmni = MSGMNI; + return; + } + + if (allowed > IPCMNI / nb_ns) { + ns->msg_ctlmni = IPCMNI / nb_ns; + return; + } + + ns->msg_ctlmni = allowed; +} + +void msg_init_ns(struct ipc_namespace *ns) +{ + ns->msg_ctlmax = MSGMAX; + ns->msg_ctlmnb = MSGMNB; + + recompute_msgmni(ns); + + 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); +} +#endif + +void __init msg_init(void) +{ + msg_init_ns(&init_ipc_ns); + + printk(KERN_INFO "msgmni has been set to %d\n", + init_ipc_ns.msg_ctlmni); + + 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); +} + +/* + * msg_lock_(check_) routines are called in the paths where the rw_mutex + * is not held. + */ +static inline struct msg_queue *msg_lock(struct ipc_namespace *ns, int id) +{ + struct kern_ipc_perm *ipcp = ipc_lock(&msg_ids(ns), id); + + if (IS_ERR(ipcp)) + return (struct msg_queue *)ipcp; + + return container_of(ipcp, struct msg_queue, q_perm); +} + +static inline struct msg_queue *msg_lock_check(struct ipc_namespace *ns, + int id) +{ + struct kern_ipc_perm *ipcp = ipc_lock_check(&msg_ids(ns), id); + + if (IS_ERR(ipcp)) + return (struct msg_queue *)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); +} + +/** + * newque - Create a new msg queue + * @ns: namespace + * @params: ptr to the structure that contains the key and msgflg + * + * Called with msg_ids.rw_mutex 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); + return retval; + } + + /* + * ipc_addid() locks msq + */ + id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni); + if (id < 0) { + security_msg_queue_free(msq); + ipc_rcu_putref(msq); + 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); + + msg_unlock(msq); + + return msq->q_perm.id; +} + +static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss) +{ + mss->tsk = current; + 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 list_head *tmp; + + tmp = h->next; + while (tmp != h) { + struct msg_sender *mss; + + mss = list_entry(tmp, struct msg_sender, list); + tmp = tmp->next; + if (kill) + mss->list.next = NULL; + wake_up_process(mss->tsk); + } +} + +static void expunge_all(struct msg_queue *msq, int res) +{ + struct list_head *tmp; + + tmp = msq->q_receivers.next; + while (tmp != &msq->q_receivers) { + struct msg_receiver *msr; + + msr = list_entry(tmp, struct msg_receiver, r_list); + tmp = tmp->next; + msr->r_msg = NULL; + wake_up_process(msr->r_tsk); + 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.rw_mutex (writer) and the spinlock for this message queue are held + * before freeque() is called. msg_ids.rw_mutex remains locked on exit. + */ +static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) +{ + struct list_head *tmp; + 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); + msg_unlock(msq); + + tmp = msq->q_messages.next; + while (tmp != &msq->q_messages) { + struct msg_msg *msg = list_entry(tmp, struct msg_msg, m_list); + + tmp = tmp->next; + atomic_dec(&ns->msg_hdrs); + free_msg(msg); + } + atomic_sub(msq->q_cbytes, &ns->msg_bytes); + security_msg_queue_free(msq); + ipc_rcu_putref(msq); +} + +/* + * Called with msg_ids.rw_mutex 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; + struct ipc_ops msg_ops; + struct ipc_params msg_params; + + ns = current->nsproxy->ipc_ns; + + msg_ops.getnew = newque; + msg_ops.associate = msg_security; + msg_ops.more_checks = NULL; + + 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 > USHORT_MAX) + out.msg_cbytes = USHORT_MAX; + else + out.msg_cbytes = in->msg_cbytes; + out.msg_lcbytes = in->msg_cbytes; + + if (in->msg_qnum > USHORT_MAX) + out.msg_qnum = USHORT_MAX; + else + out.msg_qnum = in->msg_qnum; + + if (in->msg_qbytes > USHORT_MAX) + out.msg_qbytes = USHORT_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 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 msqid64_ds msqid64; + struct msg_queue *msq; + int err; + + if (cmd == IPC_SET) { + if (copy_msqid_from_user(&msqid64, buf, version)) + return -EFAULT; + } + + ipcp = ipcctl_pre_down(&msg_ids(ns), msqid, cmd, + &msqid64.msg_perm, msqid64.msg_qbytes); + if (IS_ERR(ipcp)) + return PTR_ERR(ipcp); + + msq = container_of(ipcp, struct msg_queue, q_perm); + + 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 (msqid64.msg_qbytes > ns->msg_ctlmnb && + !capable(CAP_SYS_RESOURCE)) { + err = -EPERM; + goto out_unlock; + } + + msq->q_qbytes = msqid64.msg_qbytes; + + ipc_update_perm(&msqid64.msg_perm, ipcp); + 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; +} + +SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf) +{ + struct msg_queue *msq; + int err, 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: + { + 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).rw_mutex); + 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).rw_mutex); + if (copy_to_user(buf, &msginfo, sizeof(struct msginfo))) + return -EFAULT; + return (max_id < 0) ? 0 : max_id; + } + case MSG_STAT: /* msqid is an index rather than a msg queue id */ + case IPC_STAT: + { + struct msqid64_ds tbuf; + int success_return; + + if (!buf) + return -EFAULT; + + if (cmd == MSG_STAT) { + msq = msg_lock(ns, msqid); + if (IS_ERR(msq)) + return PTR_ERR(msq); + success_return = msq->q_perm.id; + } else { + msq = msg_lock_check(ns, msqid); + if (IS_ERR(msq)) + return PTR_ERR(msq); + success_return = 0; + } + err = -EACCES; + if (ipcperms(&msq->q_perm, S_IRUGO)) + goto out_unlock; + + err = security_msg_queue_msgctl(msq, cmd); + 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; + 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; + msg_unlock(msq); + if (copy_msqid_to_user(buf, &tbuf, version)) + return -EFAULT; + return success_return; + } + case IPC_SET: + case IPC_RMID: + err = msgctl_down(ns, msqid, cmd, buf, version); + return err; + default: + return -EINVAL; + } + +out_unlock: + msg_unlock(msq); + return err; +} + +static int testmsg(struct msg_msg *msg, long type, int mode) +{ + switch(mode) + { + case SEARCH_ANY: + 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 list_head *tmp; + + tmp = msq->q_receivers.next; + while (tmp != &msq->q_receivers) { + struct msg_receiver *msr; + + msr = list_entry(tmp, struct msg_receiver, r_list); + tmp = tmp->next; + 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) { + msr->r_msg = NULL; + wake_up_process(msr->r_tsk); + smp_mb(); + 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); + 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; + + msq = msg_lock_check(ns, msqid); + if (IS_ERR(msq)) { + err = PTR_ERR(msq); + goto out_free; + } + + for (;;) { + struct msg_sender s; + + err = -EACCES; + if (ipcperms(&msq->q_perm, S_IWUGO)) + goto out_unlock_free; + + err = security_msg_queue_msgsnd(msq, msg, msgflg); + if (err) + goto out_unlock_free; + + 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_unlock_free; + } + ss_add(msq, &s); + ipc_rcu_getref(msq); + msg_unlock(msq); + schedule(); + + ipc_lock_by_ptr(&msq->q_perm); + ipc_rcu_putref(msq); + if (msq->q_perm.deleted) { + err = -EIDRM; + goto out_unlock_free; + } + ss_del(&s); + + if (signal_pending(current)) { + err = -ERESTARTNOHAND; + goto out_unlock_free; + } + } + + msq->q_lspid = task_tgid_vnr(current); + msq->q_stime = get_seconds(); + + if (!pipelined_send(msq, msg)) { + /* noone 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_unlock_free: + msg_unlock(msq); +out_free: + 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) +{ + /* + * 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; +} + +long do_msgrcv(int msqid, long *pmtype, void __user *mtext, + size_t msgsz, long msgtyp, int msgflg) +{ + struct msg_queue *msq; + struct msg_msg *msg; + int mode; + struct ipc_namespace *ns; + + if (msqid < 0 || (long) msgsz < 0) + return -EINVAL; + mode = convert_mode(&msgtyp, msgflg); + ns = current->nsproxy->ipc_ns; + + msq = msg_lock_check(ns, msqid); + if (IS_ERR(msq)) + return PTR_ERR(msq); + + for (;;) { + struct msg_receiver msr_d; + struct list_head *tmp; + + msg = ERR_PTR(-EACCES); + if (ipcperms(&msq->q_perm, S_IRUGO)) + goto out_unlock; + + msg = ERR_PTR(-EAGAIN); + tmp = msq->q_messages.next; + while (tmp != &msq->q_messages) { + struct msg_msg *walk_msg; + + walk_msg = list_entry(tmp, struct msg_msg, m_list); + if (testmsg(walk_msg, msgtyp, mode) && + !security_msg_queue_msgrcv(msq, walk_msg, current, + msgtyp, mode)) { + + msg = walk_msg; + if (mode == SEARCH_LESSEQUAL && + walk_msg->m_type != 1) { + msg = walk_msg; + msgtyp = walk_msg->m_type - 1; + } else { + msg = walk_msg; + break; + } + } + tmp = tmp->next; + } + if (!IS_ERR(msg)) { + /* + * Found a suitable message. + * Unlink it from the queue. + */ + if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) { + msg = ERR_PTR(-E2BIG); + goto out_unlock; + } + 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); + msg_unlock(msq); + break; + } + /* No message waiting. Wait for a message */ + if (msgflg & IPC_NOWAIT) { + msg = ERR_PTR(-ENOMSG); + goto out_unlock; + } + 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 = msgsz; + msr_d.r_msg = ERR_PTR(-EAGAIN); + current->state = TASK_INTERRUPTIBLE; + msg_unlock(msq); + + 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 + * existance 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 the spin_lock() inside ipc_lock_by_ptr(). + */ + 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)) { + rcu_read_unlock(); + break; + } + + /* Lockless receive, part 3: + * Acquire the queue spinlock. + */ + ipc_lock_by_ptr(&msq->q_perm); + rcu_read_unlock(); + + /* 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_unlock; + + list_del(&msr_d.r_list); + if (signal_pending(current)) { + msg = ERR_PTR(-ERESTARTNOHAND); +out_unlock: + msg_unlock(msq); + break; + } + } + if (IS_ERR(msg)) + return PTR_ERR(msg); + + msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz; + *pmtype = msg->m_type; + if (store_msg(mtext, msg, msgsz)) + msgsz = -EFAULT; + + free_msg(msg); + + return msgsz; +} + +SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, + long, msgtyp, int, msgflg) +{ + long err, mtype; + + err = do_msgrcv(msqid, &mtype, msgp->mtext, msgsz, msgtyp, msgflg); + if (err < 0) + goto out; + + if (put_user(mtype, &msgp->mtype)) + err = -EFAULT; +out: + return err; +} + +#ifdef CONFIG_PROC_FS +static int sysvipc_msg_proc_show(struct seq_file *s, void *it) +{ + struct msg_queue *msq = it; + + return 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, + msq->q_perm.uid, + msq->q_perm.gid, + msq->q_perm.cuid, + msq->q_perm.cgid, + msq->q_stime, + msq->q_rtime, + msq->q_ctime); +} +#endif |
