ClabureDB: Classified Bug-Reports Database

   /*
    * linux/ipc/util.c
    * Copyright (C) 1992 Krishna Balasubramanian
    *
    * Sep 1997 - Call suser() last after "normal" permission checks so we
    *            get BSD style process accounting right.
    *            Occurs in several places in the IPC code.
    *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
    * Nov 1999 - ipc helper functions, unified SMP locking
   *              Manfred Spraul <manfred@colorfullife.com>
   * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
   *            Mingming Cao <cmm@us.ibm.com>
   * Mar 2006 - support for audit of ipc object properties
   *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
   * Jun 2006 - namespaces ssupport
   *            OpenVZ, SWsoft Inc.
   *            Pavel Emelianov <xemul@openvz.org>
   */
  
  #include <linux/mm.h>
  #include <linux/shm.h>
  #include <linux/init.h>
  #include <linux/msg.h>
  #include <linux/vmalloc.h>
  #include <linux/slab.h>
  #include <linux/capability.h>
  #include <linux/highuid.h>
  #include <linux/security.h>
  #include <linux/rcupdate.h>
  #include <linux/workqueue.h>
  #include <linux/seq_file.h>
  #include <linux/proc_fs.h>
  #include <linux/audit.h>
  #include <linux/nsproxy.h>
  #include <linux/rwsem.h>
  #include <linux/memory.h>
  #include <linux/ipc_namespace.h>
  
  #include <asm/unistd.h>
  
  #include "util.h"
  
  struct ipc_proc_iface {
          const char *path;
          const char *header;
          int ids;
          int (*show)(struct seq_file *, void *);
  };
  
  struct ipc_namespace init_ipc_ns = {
          .kref = {
                  .refcount        = ATOMIC_INIT(2),
          },
  };
  
  atomic_t nr_ipc_ns = ATOMIC_INIT(1);
  
  
  #ifdef CONFIG_MEMORY_HOTPLUG
  
  static void ipc_memory_notifier(struct work_struct *work)
  {
          ipcns_notify(IPCNS_MEMCHANGED);
  }
  
  static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
  
  
  static int ipc_memory_callback(struct notifier_block *self,
                                  unsigned long action, void *arg)
  {
          switch (action) {
          case MEM_ONLINE:    /* memory successfully brought online */
          case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
                  /*
                   * This is done by invoking the ipcns notifier chain with the
                   * IPC_MEMCHANGED event.
                   * In order not to keep the lock on the hotplug memory chain
                   * for too long, queue a work item that will, when waken up,
                   * activate the ipcns notification chain.
                   * No need to keep several ipc work items on the queue.
                   */
                  if (!work_pending(&ipc_memory_wq))
                          schedule_work(&ipc_memory_wq);
                  break;
          case MEM_GOING_ONLINE:
          case MEM_GOING_OFFLINE:
          case MEM_CANCEL_ONLINE:
          case MEM_CANCEL_OFFLINE:
          default:
                  break;
          }
  
          return NOTIFY_OK;
  }
  
  #endif /* CONFIG_MEMORY_HOTPLUG */
  
  /**
  *        ipc_init        -        initialise IPC subsystem
  *
  *        The various system5 IPC resources (semaphores, messages and shared
  *        memory) are initialised
  *        A callback routine is registered into the memory hotplug notifier
  *        chain: since msgmni scales to lowmem this callback routine will be
  *        called upon successful memory add / remove to recompute msmgni.
  */
  
 static int __init ipc_init(void)
 {
         sem_init();
         msg_init();
         shm_init();
         hotplug_memory_notifier(ipc_memory_callback, IPC_CALLBACK_PRI);
         register_ipcns_notifier(&init_ipc_ns);
         return 0;
 }
 __initcall(ipc_init);
 
 /**
  *        ipc_init_ids                -        initialise IPC identifiers
  *        @ids: Identifier set
  *
  *        Set up the sequence range to use for the ipc identifier range (limited
  *        below IPCMNI) then initialise the ids idr.
  */
  
 void ipc_init_ids(struct ipc_ids *ids)
 {
         init_rwsem(&ids->rw_mutex);
 
         ids->in_use = 0;
         ids->seq = 0;
         {
                 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
                 if (seq_limit > USHORT_MAX)
                         ids->seq_max = USHORT_MAX;
                  else
                          ids->seq_max = seq_limit;
         }
 
         idr_init(&ids->ipcs_idr);
 }
 
 #ifdef CONFIG_PROC_FS
 static const struct file_operations sysvipc_proc_fops;
 /**
  *        ipc_init_proc_interface        -  Create a proc interface for sysipc types using a seq_file interface.
  *        @path: Path in procfs
  *        @header: Banner to be printed at the beginning of the file.
  *        @ids: ipc id table to iterate.
  *        @show: show routine.
  */
 void __init ipc_init_proc_interface(const char *path, const char *header,
                 int ids, int (*show)(struct seq_file *, void *))
 {
         struct proc_dir_entry *pde;
         struct ipc_proc_iface *iface;
 
         iface = kmalloc(sizeof(*iface), GFP_KERNEL);
         if (!iface)
                 return;
         iface->path        = path;
         iface->header        = header;
         iface->ids        = ids;
         iface->show        = show;
 
         pde = proc_create_data(path,
                                S_IRUGO,        /* world readable */
                                NULL,           /* parent dir */
                                &sysvipc_proc_fops,
                                iface);
         if (!pde) {
                 kfree(iface);
         }
 }
 #endif
 
 /**
  *        ipc_findkey        -        find a key in an ipc identifier set        
  *        @ids: Identifier set
  *        @key: The key to find
  *        
  *        Requires ipc_ids.rw_mutex locked.
  *        Returns the LOCKED pointer to the ipc structure if found or NULL
  *        if not.
  *        If key is found ipc points to the owning ipc structure
  */
  
 static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 {
         struct kern_ipc_perm *ipc;
         int next_id;
         int total;
 
         for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
                 ipc = idr_find(&ids->ipcs_idr, next_id);
 
                 if (ipc == NULL)
                         continue;
 
                 if (ipc->key != key) {
                         total++;
                         continue;
                 }
 
                 ipc_lock_by_ptr(ipc);
                 return ipc;
         }
 
         return NULL;
 }
 
 /**
  *        ipc_get_maxid         -        get the last assigned id
  *        @ids: IPC identifier set
  *
  *        Called with ipc_ids.rw_mutex held.
  */
 
 int ipc_get_maxid(struct ipc_ids *ids)
 {
         struct kern_ipc_perm *ipc;
         int max_id = -1;
         int total, id;
 
         if (ids->in_use == 0)
                 return -1;
 
         if (ids->in_use == IPCMNI)
                 return IPCMNI - 1;
 
         /* Look for the last assigned id */
         total = 0;
         for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
                 ipc = idr_find(&ids->ipcs_idr, id);
                 if (ipc != NULL) {
                         max_id = id;
                         total++;
                 }
         }
         return max_id;
 }
 
 /**
  *        ipc_addid         -        add an IPC identifier
  *        @ids: IPC identifier set
  *        @new: new IPC permission set
  *        @size: limit for the number of used ids
  *
  *        Add an entry 'new' to the IPC ids idr. The permissions object is
  *        initialised and the first free entry is set up and the id assigned
  *        is returned. The 'new' entry is returned in a locked state on success.
  *        On failure the entry is not locked and a negative err-code is returned.
  *
  *        Called with ipc_ids.rw_mutex held as a writer.
  */
  
 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 {
         int id, err;
 
         if (size > IPCMNI)
                 size = IPCMNI;
 
         if (ids->in_use >= size)
                 return -ENOSPC;
 
         spin_lock_init(&new->lock);
         new->deleted = 0;
         rcu_read_lock();
         spin_lock(&new->lock);
 
         err = idr_get_new(&ids->ipcs_idr, new, &id);
         if (err) {
                 spin_unlock(&new->lock);
                 rcu_read_unlock();
                 return err;
         }
 
         ids->in_use++;
 
         new->cuid = new->uid = current->euid;
         new->gid = new->cgid = current->egid;
 
         new->seq = ids->seq++;
         if(ids->seq > ids->seq_max)
                 ids->seq = 0;
 
         new->id = ipc_buildid(id, new->seq);
         return id;
 }
 
 /**
  *        ipcget_new        -        create a new ipc object
  *        @ns: namespace
  *        @ids: IPC identifer set
  *        @ops: the actual creation routine to call
  *        @params: its parameters
  *
  *        This routine is called by sys_msgget, sys_semget() and sys_shmget()
  *        when the key is IPC_PRIVATE.
  */
 static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
                 struct ipc_ops *ops, struct ipc_params *params)
 {
         int err;
 retry:
         err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
 
         if (!err)
                 return -ENOMEM;
 
         down_write(&ids->rw_mutex);
         err = ops->getnew(ns, params);
         up_write(&ids->rw_mutex);
 
         if (err == -EAGAIN)
                 goto retry;
 
         return err;
 }
 
 /**
  *        ipc_check_perms        -        check security and permissions for an IPC
  *        @ipcp: ipc permission set
  *        @ops: the actual security routine to call
  *        @params: its parameters
  *
  *        This routine is called by sys_msgget(), sys_semget() and sys_shmget()
  *      when the key is not IPC_PRIVATE and that key already exists in the
  *      ids IDR.
  *
  *        On success, the IPC id is returned.
  *
  *        It is called with ipc_ids.rw_mutex and ipcp->lock held.
  */
 static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops,
                         struct ipc_params *params)
 {
         int err;
 
         if (ipcperms(ipcp, params->flg))
                 err = -EACCES;
         else {
                 err = ops->associate(ipcp, params->flg);
                 if (!err)
                         err = ipcp->id;
         }
 
         return err;
 }
 
 /**
  *        ipcget_public        -        get an ipc object or create a new one
  *        @ns: namespace
  *        @ids: IPC identifer set
  *        @ops: the actual creation routine to call
  *        @params: its parameters
  *
  *        This routine is called by sys_msgget, sys_semget() and sys_shmget()
  *        when the key is not IPC_PRIVATE.
  *        It adds a new entry if the key is not found and does some permission
  *      / security checkings if the key is found.
  *
  *        On success, the ipc id is returned.
  */
 static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
                 struct ipc_ops *ops, struct ipc_params *params)
 {
         struct kern_ipc_perm *ipcp;
         int flg = params->flg;
         int err;
 retry:
         err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
 
         /*
          * Take the lock as a writer since we are potentially going to add
          * a new entry + read locks are not "upgradable"
          */
         down_write(&ids->rw_mutex);
         ipcp = ipc_findkey(ids, params->key);
         if (ipcp == NULL) {
                 /* key not used */
                 if (!(flg & IPC_CREAT))
                         err = -ENOENT;
                 else if (!err)
                         err = -ENOMEM;
                 else
                         err = ops->getnew(ns, params);
         } else {
                 /* ipc object has been locked by ipc_findkey() */
 
                 if (flg & IPC_CREAT && flg & IPC_EXCL)
                         err = -EEXIST;
                 else {
                         err = 0;
                         if (ops->more_checks)
                                 err = ops->more_checks(ipcp, params);
                         if (!err)
                                 /*
                                  * ipc_check_perms returns the IPC id on
                                  * success
                                  */
                                 err = ipc_check_perms(ipcp, ops, params);
                 }
                 ipc_unlock(ipcp);
         }
         up_write(&ids->rw_mutex);
 
         if (err == -EAGAIN)
                 goto retry;
 
         return err;
 }
 
 
 /**
  *        ipc_rmid        -        remove an IPC identifier
  *        @ids: IPC identifier set
  *        @ipcp: ipc perm structure containing the identifier to remove
  *
  *        ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
  *        before this function is called, and remain locked on the exit.
  */
  
 void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 {
         int lid = ipcid_to_idx(ipcp->id);
 
         idr_remove(&ids->ipcs_idr, lid);
 
         ids->in_use--;
 
         ipcp->deleted = 1;
 
         return;
 }
 
 /**
  *        ipc_alloc        -        allocate ipc space
  *        @size: size desired
  *
  *        Allocate memory from the appropriate pools and return a pointer to it.
  *        NULL is returned if the allocation fails
  */
  
 void* ipc_alloc(int size)
 {
         void* out;
         if(size > PAGE_SIZE)
                 out = vmalloc(size);
         else
                 out = kmalloc(size, GFP_KERNEL);
         return out;
 }
 
 /**
  *        ipc_free        -       free ipc space
  *        @ptr: pointer returned by ipc_alloc
  *        @size: size of block
  *
  *        Free a block created with ipc_alloc(). The caller must know the size
  *        used in the allocation call.
  */
 
 void ipc_free(void* ptr, int size)
 {
         if(size > PAGE_SIZE)
                 vfree(ptr);
         else
                 kfree(ptr);
 }
 
 /*
  * rcu allocations:
  * There are three headers that are prepended to the actual allocation:
  * - during use: ipc_rcu_hdr.
  * - during the rcu grace period: ipc_rcu_grace.
  * - [only if vmalloc]: ipc_rcu_sched.
  * Their lifetime doesn't overlap, thus the headers share the same memory.
  * Unlike a normal union, they are right-aligned, thus some container_of
  * forward/backward casting is necessary:
  */
 struct ipc_rcu_hdr
 {
         int refcount;
         int is_vmalloc;
         void *data[0];
 };
 
 
 struct ipc_rcu_grace
 {
         struct rcu_head rcu;
         /* "void *" makes sure alignment of following data is sane. */
         void *data[0];
 };
 
 struct ipc_rcu_sched
 {
         struct work_struct work;
         /* "void *" makes sure alignment of following data is sane. */
         void *data[0];
 };
 
 #define HDRLEN_KMALLOC                (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
                                         sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
 #define HDRLEN_VMALLOC                (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
                                         sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
 
 static inline int rcu_use_vmalloc(int size)
 {
         /* Too big for a single page? */
         if (HDRLEN_KMALLOC + size > PAGE_SIZE)
                 return 1;
         return 0;
 }
 
 /**
  *        ipc_rcu_alloc        -        allocate ipc and rcu space 
  *        @size: size desired
  *
  *        Allocate memory for the rcu header structure +  the object.
  *        Returns the pointer to the object.
  *        NULL is returned if the allocation fails. 
  */
  
 void* ipc_rcu_alloc(int size)
 {
         void* out;
         /* 
          * We prepend the allocation with the rcu struct, and
          * workqueue if necessary (for vmalloc). 
          */
         if (rcu_use_vmalloc(size)) {
                 out = vmalloc(HDRLEN_VMALLOC + size);
                 if (out) {
                         out += HDRLEN_VMALLOC;
                         container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
                         container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
                 }
         } else {
                 out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
                 if (out) {
                         out += HDRLEN_KMALLOC;
                         container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
                         container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
                 }
         }
 
         return out;
 }
 
 void ipc_rcu_getref(void *ptr)
 {
         container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
 }
 
 static void ipc_do_vfree(struct work_struct *work)
 {
         vfree(container_of(work, struct ipc_rcu_sched, work));
 }
 
 /**
  * ipc_schedule_free - free ipc + rcu space
  * @head: RCU callback structure for queued work
  * 
  * Since RCU callback function is called in bh,
  * we need to defer the vfree to schedule_work().
  */
 static void ipc_schedule_free(struct rcu_head *head)
 {
         struct ipc_rcu_grace *grace;
         struct ipc_rcu_sched *sched;
 
         grace = container_of(head, struct ipc_rcu_grace, rcu);
         sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
                                 data[0]);
 
         INIT_WORK(&sched->work, ipc_do_vfree);
         schedule_work(&sched->work);
 }
 
 /**
  * ipc_immediate_free - free ipc + rcu space
  * @head: RCU callback structure that contains pointer to be freed
  *
  * Free from the RCU callback context.
  */
 static void ipc_immediate_free(struct rcu_head *head)
 {
         struct ipc_rcu_grace *free =
                 container_of(head, struct ipc_rcu_grace, rcu);
         kfree(free);
 }
 
 void ipc_rcu_putref(void *ptr)
 {
         if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
                 return;
 
         if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
                 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
                                 ipc_schedule_free);
         } else {
                 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
                                 ipc_immediate_free);
         }
 }
 
 /**
  *        ipcperms        -        check IPC permissions
  *        @ipcp: IPC permission set
  *        @flag: desired permission set.
  *
  *        Check user, group, other permissions for access
  *        to ipc resources. return 0 if allowed
  */
  
 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
 {        /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
         int requested_mode, granted_mode, err;
 
         if (unlikely((err = audit_ipc_obj(ipcp))))
                 return err;
         requested_mode = (flag >> 6) | (flag >> 3) | flag;
         granted_mode = ipcp->mode;
         if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
                 granted_mode >>= 6;
         else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
                 granted_mode >>= 3;
         /* is there some bit set in requested_mode but not in granted_mode? */
         if ((requested_mode & ~granted_mode & 0007) && 
             !capable(CAP_IPC_OWNER))
                 return -1;
 
         return security_ipc_permission(ipcp, flag);
 }
 
 /*
  * Functions to convert between the kern_ipc_perm structure and the
  * old/new ipc_perm structures
  */
 
 /**
  *        kernel_to_ipc64_perm        -        convert kernel ipc permissions to user
  *        @in: kernel permissions
  *        @out: new style IPC permissions
  *
  *        Turn the kernel object @in into a set of permissions descriptions
  *        for returning to userspace (@out).
  */
  
 
 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 {
         out->key        = in->key;
         out->uid        = in->uid;
         out->gid        = in->gid;
         out->cuid        = in->cuid;
         out->cgid        = in->cgid;
         out->mode        = in->mode;
         out->seq        = in->seq;
 }
 
 /**
  *        ipc64_perm_to_ipc_perm        -        convert new ipc permissions to old
  *        @in: new style IPC permissions
  *        @out: old style IPC permissions
  *
  *        Turn the new style permissions object @in into a compatibility
  *        object and store it into the @out pointer.
  */
  
 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 {
         out->key        = in->key;
         SET_UID(out->uid, in->uid);
         SET_GID(out->gid, in->gid);
         SET_UID(out->cuid, in->cuid);
         SET_GID(out->cgid, in->cgid);
         out->mode        = in->mode;
         out->seq        = in->seq;
 }
 
 /**
  * ipc_lock - Lock an ipc structure without rw_mutex held
  * @ids: IPC identifier set
  * @id: ipc id to look for
  *
  * Look for an id in the ipc ids idr and lock the associated ipc object.
  *
  * The ipc object is locked on exit.
  */
 
 struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 {
         struct kern_ipc_perm *out;
         int lid = ipcid_to_idx(id);
 
         rcu_read_lock();
         out = idr_find(&ids->ipcs_idr, lid);
         if (out == NULL) {
                 rcu_read_unlock();
                 return ERR_PTR(-EINVAL);
         }
 
         spin_lock(&out->lock);
         
         /* ipc_rmid() may have already freed the ID while ipc_lock
          * was spinning: here verify that the structure is still valid
          */
         if (out->deleted) {
                 spin_unlock(&out->lock);
                 rcu_read_unlock();
                 return ERR_PTR(-EINVAL);
         }
 
         return out;
 }
 
 struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
 {
         struct kern_ipc_perm *out;
 
         out = ipc_lock(ids, id);
         if (IS_ERR(out))
                 return out;
 
         if (ipc_checkid(out, id)) {
                 ipc_unlock(out);
                 return ERR_PTR(-EIDRM);
         }
 
         return out;
 }
 
 /**
  * ipcget - Common sys_*get() code
  * @ns : namsepace
  * @ids : IPC identifier set
  * @ops : operations to be called on ipc object creation, permission checks
  *        and further checks
  * @params : the parameters needed by the previous operations.
  *
  * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
  */
 int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
                         struct ipc_ops *ops, struct ipc_params *params)
 {
         if (params->key == IPC_PRIVATE)
                 return ipcget_new(ns, ids, ops, params);
         else
                 return ipcget_public(ns, ids, ops, params);
 }
 
 /**
  * ipc_update_perm - update the permissions of an IPC.
  * @in:  the permission given as input.
  * @out: the permission of the ipc to set.
  */
 void ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 {
         out->uid = in->uid;
         out->gid = in->gid;
         out->mode = (out->mode & ~S_IRWXUGO)
                 | (in->mode & S_IRWXUGO);
 }
 
 /**
  * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
  * @ids:  the table of ids where to look for the ipc
  * @id:   the id of the ipc to retrieve
  * @cmd:  the cmd to check
  * @perm: the permission to set
  * @extra_perm: one extra permission parameter used by msq
  *
  * This function does some common audit and permissions check for some IPC_XXX
  * cmd and is called from semctl_down, shmctl_down and msgctl_down.
  * It must be called without any lock held and
  *  - retrieves the ipc with the given id in the given table.
  *  - performs some audit and permission check, depending on the given cmd
  *  - returns the ipc with both ipc and rw_mutex locks held in case of success
  *    or an err-code without any lock held otherwise.
  */
 struct kern_ipc_perm *ipcctl_pre_down(struct ipc_ids *ids, int id, int cmd,
                                       struct ipc64_perm *perm, int extra_perm)
 {
         struct kern_ipc_perm *ipcp;
         int err;
 
         down_write(&ids->rw_mutex);
         ipcp = ipc_lock_check(ids, id);
         if (IS_ERR(ipcp)) {
                 err = PTR_ERR(ipcp);
                 goto out_up;
         }
 
         err = audit_ipc_obj(ipcp);
         if (err)
                 goto out_unlock;
 
         if (cmd == IPC_SET) {
                 err = audit_ipc_set_perm(extra_perm, perm->uid,
                                          perm->gid, perm->mode);
                 if (err)
                         goto out_unlock;
         }
         if (current->euid == ipcp->cuid ||
             current->euid == ipcp->uid || capable(CAP_SYS_ADMIN))
                 return ipcp;
 
         err = -EPERM;
 out_unlock:
         ipc_unlock(ipcp);
 out_up:
         up_write(&ids->rw_mutex);
         return ERR_PTR(err);
 }
 
 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
 
 
 /**
  *        ipc_parse_version        -        IPC call version
  *        @cmd: pointer to command
  *
  *        Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
  *        The @cmd value is turned from an encoding command and version into
  *        just the command code.
  */
  
 int ipc_parse_version (int *cmd)
 {
         if (*cmd & IPC_64) {
                 *cmd ^= IPC_64;
                 return IPC_64;
         } else {
                 return IPC_OLD;
         }
 }
 
 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */
 
 #ifdef CONFIG_PROC_FS
 struct ipc_proc_iter {
         struct ipc_namespace *ns;
         struct ipc_proc_iface *iface;
 };
 
 /*
  * This routine locks the ipc structure found at least at position pos.
  */
 static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
                                               loff_t *new_pos)
 {
         struct kern_ipc_perm *ipc;
         int total, id;
 
         total = 0;
         for (id = 0; id < pos && total < ids->in_use; id++) {
                 ipc = idr_find(&ids->ipcs_idr, id);
                 if (ipc != NULL)
                         total++;
         }
 
         if (total >= ids->in_use)
                 return NULL;
 
         for ( ; pos < IPCMNI; pos++) {
                 ipc = idr_find(&ids->ipcs_idr, pos);
                 if (ipc != NULL) {
                         *new_pos = pos + 1;
                         ipc_lock_by_ptr(ipc);
                         return ipc;
                 }
         }
 
         /* Out of range - return NULL to terminate iteration */
         return NULL;
 }
 
 static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 {
         struct ipc_proc_iter *iter = s->private;
         struct ipc_proc_iface *iface = iter->iface;
         struct kern_ipc_perm *ipc = it;
 
         /* If we had an ipc id locked before, unlock it */
         if (ipc && ipc != SEQ_START_TOKEN)
                 ipc_unlock(ipc);
 
         return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 }
 
 /*
  * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
  * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
  */
 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 {
         struct ipc_proc_iter *iter = s->private;
         struct ipc_proc_iface *iface = iter->iface;
         struct ipc_ids *ids;
 
         ids = &iter->ns->ids[iface->ids];
 
         /*
          * Take the lock - this will be released by the corresponding
          * call to stop().
          */
         down_read(&ids->rw_mutex);
 
         /* pos < 0 is invalid */
         if (*pos < 0)
                 return NULL;
 
         /* pos == 0 means header */
         if (*pos == 0)
                 return SEQ_START_TOKEN;
 
         /* Find the (pos-1)th ipc */
         return sysvipc_find_ipc(ids, *pos - 1, pos);
 }
 
 static void sysvipc_proc_stop(struct seq_file *s, void *it)
 {
         struct kern_ipc_perm *ipc = it;
         struct ipc_proc_iter *iter = s->private;
         struct ipc_proc_iface *iface = iter->iface;
         struct ipc_ids *ids;
 
         /* If we had a locked structure, release it */
         if (ipc && ipc != SEQ_START_TOKEN)
                 ipc_unlock(ipc);
 
         ids = &iter->ns->ids[iface->ids];
         /* Release the lock we took in start() */
         up_read(&ids->rw_mutex);
 }
 
 static int sysvipc_proc_show(struct seq_file *s, void *it)
 {
         struct ipc_proc_iter *iter = s->private;
         struct ipc_proc_iface *iface = iter->iface;
 
         if (it == SEQ_START_TOKEN)
                 return seq_puts(s, iface->header);
 
         return iface->show(s, it);
 }
 
 static struct seq_operations sysvipc_proc_seqops = {
         .start = sysvipc_proc_start,
         .stop  = sysvipc_proc_stop,
         .next  = sysvipc_proc_next,
         .show  = sysvipc_proc_show,
 };
 
 static int sysvipc_proc_open(struct inode *inode, struct file *file)
 {
         int ret;
         struct seq_file *seq;
         struct ipc_proc_iter *iter;
 
         ret = -ENOMEM;
         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
         if (!iter)
                 goto out;
 
         ret = seq_open(file, &sysvipc_proc_seqops);
         if (ret)
                 goto out_kfree;
 
         seq = file->private_data;
         seq->private = iter;
 
         iter->iface = PDE(inode)->data;
         iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 out:
         return ret;
 out_kfree:
         kfree(iter);
         goto out;
 }
 
 static int sysvipc_proc_release(struct inode *inode, struct file *file)
 {
         struct seq_file *seq = file->private_data;
         struct ipc_proc_iter *iter = seq->private;
         put_ipc_ns(iter->ns);
         return seq_release_private(inode, file);
 }
 
 static const struct file_operations sysvipc_proc_fops = {
         .open    = sysvipc_proc_open,
         .read    = seq_read,
         .llseek  = seq_lseek,
        .release = sysvipc_proc_release,
};
#endif /* CONFIG_PROC_FS */