IPC之msg.c源码解读
// SPDX-License-Identifier: GPL-2.0 /* * 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/wake_q.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 <linux/rhashtable.h> #include <asm/current.h> #include <linux/uaccess.h> #include "util.h" /* one msq_queue structure for each present queue on the system */ struct msg_queue { struct kern_ipc_perm q_perm; time64_t q_stime; /* last msgsnd time */ time64_t q_rtime; /* last msgrcv time */ time64_t q_ctime; /* last change time */ unsigned long q_cbytes; /* current number of bytes on queue */ unsigned long q_qnum; /* number of messages in queue */ unsigned long q_qbytes; /* max number of bytes on queue */ struct pid *q_lspid; /* pid of last msgsnd */ struct pid *q_lrpid; /* last receive pid */ struct list_head q_messages; struct list_head q_receivers; struct list_head q_senders; } __randomize_layout; /* 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 *r_msg; }; /* one msg_sender for each sleeping sender */ struct msg_sender { struct list_head list; struct task_struct *tsk; size_t msgsz; }; #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_idr(&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 kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu); struct msg_queue *msq = container_of(p, struct msg_queue, q_perm); security_msg_queue_free(&msq->q_perm); kvfree(msq); } /** * 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 retval; key_t key = params->key; int msgflg = params->flg; msq = kvmalloc(sizeof(*msq), GFP_KERNEL); if (unlikely(!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->q_perm); if (retval) { kvfree(msq); return retval; } msq->q_stime = msq->q_rtime = 0; msq->q_ctime = ktime_get_real_seconds(); msq->q_cbytes = msq->q_qnum = 0; msq->q_qbytes = ns->msg_ctlmnb; msq->q_lspid = msq->q_lrpid = NULL; INIT_LIST_HEAD(&msq->q_messages); INIT_LIST_HEAD(&msq->q_receivers); INIT_LIST_HEAD(&msq->q_senders); /* ipc_addid() locks msq upon success. */ retval = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni); if (retval < 0) { ipc_rcu_putref(&msq->q_perm, msg_rcu_free); return retval; } ipc_unlock_object(&msq->q_perm); rcu_read_unlock(); return msq->q_perm.id; } static inline bool msg_fits_inqueue(struct msg_queue *msq, size_t msgsz) { return msgsz + msq->q_cbytes <= msq->q_qbytes && 1 + msq->q_qnum <= msq->q_qbytes; } static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss, size_t msgsz) { mss->tsk = current; mss->msgsz = msgsz; __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) list_del(&mss->list); } static void ss_wakeup(struct msg_queue *msq, struct wake_q_head *wake_q, bool kill) { struct msg_sender *mss, *t; struct task_struct *stop_tsk = NULL; struct list_head *h = &msq->q_senders; list_for_each_entry_safe(mss, t, h, list) { if (kill) mss->list.next = NULL; /* * Stop at the first task we don't wakeup, * we've already iterated the original * sender queue. */ else if (stop_tsk == mss->tsk) break; /* * We are not in an EIDRM scenario here, therefore * verify that we really need to wakeup the task. * To maintain current semantics and wakeup order, * move the sender to the tail on behalf of the * blocked task. */ else if (!msg_fits_inqueue(msq, mss->msgsz)) { if (!stop_tsk) stop_tsk = mss->tsk; list_move_tail(&mss->list, &msq->q_senders); continue; } wake_q_add(wake_q, mss->tsk); } } static void expunge_all(struct msg_queue *msq, int res, struct wake_q_head *wake_q) { struct msg_receiver *msr, *t; list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) { wake_q_add(wake_q, msr->r_tsk); WRITE_ONCE(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); DEFINE_WAKE_Q(wake_q); expunge_all(msq, -EIDRM, &wake_q); ss_wakeup(msq, &wake_q, true); msg_rmid(ns, msq); ipc_unlock_object(&msq->q_perm); wake_up_q(&wake_q); 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_update_pid(&msq->q_lspid, NULL); ipc_update_pid(&msq->q_lrpid, NULL); ipc_rcu_putref(&msq->q_perm, msg_rcu_free); } long ksys_msgget(key_t key, int msgflg) { struct ipc_namespace *ns; static const struct ipc_ops msg_ops = { .getnew = newque, .associate = security_msg_queue_associate, }; 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); } SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg) { return ksys_msgget(key, msgflg); } 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 msqid64_ds *msqid64) { struct kern_ipc_perm *ipcp; struct msg_queue *msq; int err; down_write(&msg_ids(ns).rwsem); rcu_read_lock(); ipcp = ipcctl_obtain_check(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->q_perm, 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: { DEFINE_WAKE_Q(wake_q); 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 = ktime_get_real_seconds(); /* * Sleeping receivers might be excluded by * stricter permissions. */ expunge_all(msq, -EAGAIN, &wake_q); /* * Sleeping senders might be able to send * due to a larger queue size. */ ss_wakeup(msq, &wake_q, false); ipc_unlock_object(&msq->q_perm); wake_up_q(&wake_q); goto out_unlock1; } 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_info(struct ipc_namespace *ns, int msqid, int cmd, struct msginfo *msginfo) { int err; int max_idx; /* * 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_idx = ipc_get_maxidx(&msg_ids(ns)); up_read(&msg_ids(ns).rwsem); return (max_idx < 0) ? 0 : max_idx; } static int msgctl_stat(struct ipc_namespace *ns, int msqid, int cmd, struct msqid64_ds *p) { struct msg_queue *msq; int err; memset(p, 0, sizeof(*p)); rcu_read_lock(); if (cmd == MSG_STAT || cmd == MSG_STAT_ANY) { msq = msq_obtain_object(ns, msqid); if (IS_ERR(msq)) { err = PTR_ERR(msq); goto out_unlock; } } else { /* IPC_STAT */ msq = msq_obtain_object_check(ns, msqid); if (IS_ERR(msq)) { err = PTR_ERR(msq); goto out_unlock; } } /* see comment for SHM_STAT_ANY */ if (cmd == MSG_STAT_ANY) audit_ipc_obj(&msq->q_perm); else { err = -EACCES; if (ipcperms(ns, &msq->q_perm, S_IRUGO)) goto out_unlock; } err = security_msg_queue_msgctl(&msq->q_perm, cmd); if (err) goto out_unlock; ipc_lock_object(&msq->q_perm); if (!ipc_valid_object(&msq->q_perm)) { ipc_unlock_object(&msq->q_perm); err = -EIDRM; goto out_unlock; } kernel_to_ipc64_perm(&msq->q_perm, &p->msg_perm); p->msg_stime = msq->q_stime; p->msg_rtime = msq->q_rtime; p->msg_ctime = msq->q_ctime; #ifndef CONFIG_64BIT p->msg_stime_high = msq->q_stime >> 32; p->msg_rtime_high = msq->q_rtime >> 32; p->msg_ctime_high = msq->q_ctime >> 32; #endif p->msg_cbytes = msq->q_cbytes; p->msg_qnum = msq->q_qnum; p->msg_qbytes = msq->q_qbytes; p->msg_lspid = pid_vnr(msq->q_lspid); p->msg_lrpid = pid_vnr(msq->q_lrpid); if (cmd == IPC_STAT) { /* * As defined in SUS: * Return 0 on success */ err = 0; } else { /* * MSG_STAT and MSG_STAT_ANY (both Linux specific) * Return the full id, including the sequence number */ err = msq->q_perm.id; } ipc_unlock_object(&msq->q_perm); out_unlock: rcu_read_unlock(); return err; } static long ksys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf, int version) { struct ipc_namespace *ns; struct msqid64_ds msqid64; int err; if (msqid < 0 || cmd < 0) return -EINVAL; ns = current->nsproxy->ipc_ns; switch (cmd) { case IPC_INFO: case MSG_INFO: { struct msginfo msginfo; err = msgctl_info(ns, msqid, cmd, &msginfo); if (err < 0) return err; if (copy_to_user(buf, &msginfo, sizeof(struct msginfo))) err = -EFAULT; return err; } case MSG_STAT: /* msqid is an index rather than a msg queue id */ case MSG_STAT_ANY: case IPC_STAT: err = msgctl_stat(ns, msqid, cmd, &msqid64); if (err < 0) return err; if (copy_msqid_to_user(buf, &msqid64, version)) err = -EFAULT; return err; case IPC_SET: if (copy_msqid_from_user(&msqid64, buf, version)) return -EFAULT; /* fallthru */ case IPC_RMID: return msgctl_down(ns, msqid, cmd, &msqid64); default: return -EINVAL; } } SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf) { return ksys_msgctl(msqid, cmd, buf, IPC_64); } #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION long ksys_old_msgctl(int msqid, int cmd, struct msqid_ds __user *buf) { int version = ipc_parse_version(&cmd); return ksys_msgctl(msqid, cmd, buf, version); } SYSCALL_DEFINE3(old_msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf) { return ksys_old_msgctl(msqid, cmd, buf); } #endif #ifdef CONFIG_COMPAT struct compat_msqid_ds { struct compat_ipc_perm msg_perm; compat_uptr_t msg_first; compat_uptr_t msg_last; old_time32_t msg_stime; old_time32_t msg_rtime; old_time32_t msg_ctime; compat_ulong_t msg_lcbytes; compat_ulong_t msg_lqbytes; unsigned short msg_cbytes; unsigned short msg_qnum; unsigned short msg_qbytes; compat_ipc_pid_t msg_lspid; compat_ipc_pid_t msg_lrpid; }; static int copy_compat_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version) { memset(out, 0, sizeof(*out)); if (version == IPC_64) { struct compat_msqid64_ds __user *p = buf; if (get_compat_ipc64_perm(&out->msg_perm, &p->msg_perm)) return -EFAULT; if (get_user(out->msg_qbytes, &p->msg_qbytes)) return -EFAULT; } else { struct compat_msqid_ds __user *p = buf; if (get_compat_ipc_perm(&out->msg_perm, &p->msg_perm)) return -EFAULT; if (get_user(out->msg_qbytes, &p->msg_qbytes)) return -EFAULT; } return 0; } static int copy_compat_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version) { if (version == IPC_64) { struct compat_msqid64_ds v; memset(&v, 0, sizeof(v)); to_compat_ipc64_perm(&v.msg_perm, &in->msg_perm); v.msg_stime = lower_32_bits(in->msg_stime); v.msg_stime_high = upper_32_bits(in->msg_stime); v.msg_rtime = lower_32_bits(in->msg_rtime); v.msg_rtime_high = upper_32_bits(in->msg_rtime); v.msg_ctime = lower_32_bits(in->msg_ctime); v.msg_ctime_high = upper_32_bits(in->msg_ctime); v.msg_cbytes = in->msg_cbytes; v.msg_qnum = in->msg_qnum; v.msg_qbytes = in->msg_qbytes; v.msg_lspid = in->msg_lspid; v.msg_lrpid = in->msg_lrpid; return copy_to_user(buf, &v, sizeof(v)); } else { struct compat_msqid_ds v; memset(&v, 0, sizeof(v)); to_compat_ipc_perm(&v.msg_perm, &in->msg_perm); v.msg_stime = in->msg_stime; v.msg_rtime = in->msg_rtime; v.msg_ctime = in->msg_ctime; v.msg_cbytes = in->msg_cbytes; v.msg_qnum = in->msg_qnum; v.msg_qbytes = in->msg_qbytes; v.msg_lspid = in->msg_lspid; v.msg_lrpid = in->msg_lrpid; return copy_to_user(buf, &v, sizeof(v)); } } static long compat_ksys_msgctl(int msqid, int cmd, void __user *uptr, int version) { struct ipc_namespace *ns; int err; struct msqid64_ds msqid64; ns = current->nsproxy->ipc_ns; if (msqid < 0 || cmd < 0) return -EINVAL; switch (cmd & (~IPC_64)) { case IPC_INFO: case MSG_INFO: { struct msginfo msginfo; err = msgctl_info(ns, msqid, cmd, &msginfo); if (err < 0) return err; if (copy_to_user(uptr, &msginfo, sizeof(struct msginfo))) err = -EFAULT; return err; } case IPC_STAT: case MSG_STAT: case MSG_STAT_ANY: err = msgctl_stat(ns, msqid, cmd, &msqid64); if (err < 0) return err; if (copy_compat_msqid_to_user(uptr, &msqid64, version)) err = -EFAULT; return err; case IPC_SET: if (copy_compat_msqid_from_user(&msqid64, uptr, version)) return -EFAULT; /* fallthru */ case IPC_RMID: return msgctl_down(ns, msqid, cmd, &msqid64); default: return -EINVAL; } } COMPAT_SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, void __user *, uptr) { return compat_ksys_msgctl(msqid, cmd, uptr, IPC_64); } #ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION long compat_ksys_old_msgctl(int msqid, int cmd, void __user *uptr) { int version = compat_ipc_parse_version(&cmd); return compat_ksys_msgctl(msqid, cmd, uptr, version); } COMPAT_SYSCALL_DEFINE3(old_msgctl, int, msqid, int, cmd, void __user *, uptr) { return compat_ksys_old_msgctl(msqid, cmd, uptr); } #endif #endif 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 wake_q_head *wake_q) { 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->q_perm, msg, msr->r_tsk, msr->r_msgtype, msr->r_mode)) { list_del(&msr->r_list); if (msr->r_maxsize < msg->m_ts) { wake_q_add(wake_q, msr->r_tsk); WRITE_ONCE(msr->r_msg, ERR_PTR(-E2BIG)); } else { ipc_update_pid(&msq->q_lrpid, task_pid(msr->r_tsk)); msq->q_rtime = ktime_get_real_seconds(); wake_q_add(wake_q, msr->r_tsk); WRITE_ONCE(msr->r_msg, msg); return 1; } } } return 0; } static 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; DEFINE_WAKE_Q(wake_q); 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->q_perm, msg, msgflg); if (err) goto out_unlock0; if (msg_fits_inqueue(msq, msgsz)) break; /* queue full, wait: */ if (msgflg & IPC_NOWAIT) { err = -EAGAIN; goto out_unlock0; } /* enqueue the sender and prepare to block */ ss_add(msq, &s, msgsz); if (!ipc_rcu_getref(&msq->q_perm)) { 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->q_perm, msg_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; } } ipc_update_pid(&msq->q_lspid, task_tgid(current)); msq->q_stime = ktime_get_real_seconds(); if (!pipelined_send(msq, msg, &wake_q)) { /* 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); wake_up_q(&wake_q); out_unlock1: rcu_read_unlock(); if (msg != NULL) free_msg(msg); return err; } long ksys_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); } SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, int, msgflg) { return ksys_msgsnd(msqid, msgp, msgsz, msgflg); } #ifdef CONFIG_COMPAT struct compat_msgbuf { compat_long_t mtype; char mtext[1]; }; long compat_ksys_msgsnd(int msqid, compat_uptr_t msgp, compat_ssize_t msgsz, int msgflg) { struct compat_msgbuf __user *up = compat_ptr(msgp); compat_long_t mtype; if (get_user(mtype, &up->mtype)) return -EFAULT; return do_msgsnd(msqid, mtype, up->mtext, (ssize_t)msgsz, msgflg); } COMPAT_SYSCALL_DEFINE4(msgsnd, int, msqid, compat_uptr_t, msgp, compat_ssize_t, msgsz, int, msgflg) { return compat_ksys_msgsnd(msqid, msgp, msgsz, msgflg); } #endif 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) { if (*msgtyp == LONG_MIN) /* -LONG_MIN is undefined */ *msgtyp = LONG_MAX; else *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->q_perm, 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); } static 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; DEFINE_WAKE_Q(wake_q); 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 = ktime_get_real_seconds(); ipc_update_pid(&msq->q_lrpid, task_tgid(current)); msq->q_cbytes -= msg->m_ts; atomic_sub(msg->m_ts, &ns->msg_bytes); atomic_dec(&ns->msg_hdrs); ss_wakeup(msq, &wake_q, false); 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: * 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(); /* * Lockless receive, part 2: * The work in pipelined_send() and expunge_all(): * - Set pointer to message * - Queue the receiver task for later wakeup * - Wake up the process after the lock is dropped. * * Should the process wake up before this wakeup (due to a * signal) it will either see the message and continue ... */ msg = READ_ONCE(msr_d.r_msg); if (msg != ERR_PTR(-EAGAIN)) goto out_unlock1; /* * ... or see -EAGAIN, acquire the lock to check the message * again. */ ipc_lock_object(&msq->q_perm); 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); wake_up_q(&wake_q); 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; } long ksys_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); } SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, long, msgtyp, int, msgflg) { return ksys_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg); } #ifdef CONFIG_COMPAT static long compat_do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz) { struct compat_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; } long compat_ksys_msgrcv(int msqid, compat_uptr_t msgp, compat_ssize_t msgsz, compat_long_t msgtyp, int msgflg) { return do_msgrcv(msqid, compat_ptr(msgp), (ssize_t)msgsz, (long)msgtyp, msgflg, compat_do_msg_fill); } COMPAT_SYSCALL_DEFINE5(msgrcv, int, msqid, compat_uptr_t, msgp, compat_ssize_t, msgsz, compat_long_t, msgtyp, int, msgflg) { return compat_ksys_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg); } #endif 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); rhashtable_destroy(&ns->ids[IPC_MSG_IDS].key_ht); } #endif #ifdef CONFIG_PROC_FS static int sysvipc_msg_proc_show(struct seq_file *s, void *it) { struct pid_namespace *pid_ns = ipc_seq_pid_ns(s); struct user_namespace *user_ns = seq_user_ns(s); struct kern_ipc_perm *ipcp = it; struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm); seq_printf(s, "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10llu %10llu %10llu\n", msq->q_perm.key, msq->q_perm.id, msq->q_perm.mode, msq->q_cbytes, msq->q_qnum, pid_nr_ns(msq->q_lspid, pid_ns), pid_nr_ns(msq->q_lrpid, pid_ns), 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); }