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shm.c

/*
 * linux/ipc/shm.c
 * Copyright (C) 1992, 1993 Krishna Balasubramanian
 *     Many improvements/fixes by Bruno Haible.
 * Replaced `struct shm_desc' by `struct vm_area_struct', July 1994.
 * Fixed the shm swap deallocation (shm_unuse()), August 1998 Andrea Arcangeli.
 *
 * /proc/sysvipc/shm support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
 * BIGMEM support, Andrea Arcangeli <andrea@suse.de>
 * SMP thread shm, Jean-Luc Boyard <jean-luc.boyard@siemens.fr>
 * HIGHMEM support, Ingo Molnar <mingo@redhat.com>
 * Make shmmax, shmall, shmmni sysctl'able, Christoph Rohland <cr@sap.com>
 * Shared /dev/zero support, Kanoj Sarcar <kanoj@sgi.com>
 * Move the mm functionality over to mm/shmem.c, Christoph Rohland <cr@sap.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/slab.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/shm.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/shmem_fs.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/ptrace.h>
#include <linux/seq_file.h>
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
#include <linux/mount.h>

#include <asm/uaccess.h>

#include "util.h"

struct shm_file_data {
      int id;
      struct ipc_namespace *ns;
      struct file *file;
      const struct vm_operations_struct *vm_ops;
};

#define shm_file_data(file) (*((struct shm_file_data **)&(file)->private_data))

static const struct file_operations shm_file_operations;
static struct vm_operations_struct shm_vm_ops;

static struct ipc_ids init_shm_ids;

#define shm_ids(ns)     (*((ns)->ids[IPC_SHM_IDS]))

#define shm_unlock(shp)             \
      ipc_unlock(&(shp)->shm_perm)
#define shm_buildid(id, seq)  ipc_buildid(id, seq)

static int newseg(struct ipc_namespace *, struct ipc_params *);
static void shm_open(struct vm_area_struct *vma);
static void shm_close(struct vm_area_struct *vma);
static void shm_destroy (struct ipc_namespace *ns, struct shmid_kernel *shp);
#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it);
#endif

static void __shm_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids)
{
      ns->ids[IPC_SHM_IDS] = ids;
      ns->shm_ctlmax = SHMMAX;
      ns->shm_ctlall = SHMALL;
      ns->shm_ctlmni = SHMMNI;
      ns->shm_tot = 0;
      ipc_init_ids(ids);
}

/*
 * Called with shm_ids.rw_mutex (writer) and the shp structure locked.
 * Only shm_ids.rw_mutex remains locked on exit.
 */
static void do_shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *shp)
{
      if (shp->shm_nattch){
            shp->shm_perm.mode |= SHM_DEST;
            /* Do not find it any more */
            shp->shm_perm.key = IPC_PRIVATE;
            shm_unlock(shp);
      } else
            shm_destroy(ns, shp);
}

int shm_init_ns(struct ipc_namespace *ns)
{
      struct ipc_ids *ids;

      ids = kmalloc(sizeof(struct ipc_ids), GFP_KERNEL);
      if (ids == NULL)
            return -ENOMEM;

      __shm_init_ns(ns, ids);
      return 0;
}

void shm_exit_ns(struct ipc_namespace *ns)
{
      struct shmid_kernel *shp;
      int next_id;
      int total, in_use;

      down_write(&shm_ids(ns).rw_mutex);

      in_use = shm_ids(ns).in_use;

      for (total = 0, next_id = 0; total < in_use; next_id++) {
            shp = idr_find(&shm_ids(ns).ipcs_idr, next_id);
            if (shp == NULL)
                  continue;
            ipc_lock_by_ptr(&shp->shm_perm);
            do_shm_rmid(ns, shp);
            total++;
      }
      up_write(&shm_ids(ns).rw_mutex);

      kfree(ns->ids[IPC_SHM_IDS]);
      ns->ids[IPC_SHM_IDS] = NULL;
}

void __init shm_init (void)
{
      __shm_init_ns(&init_ipc_ns, &init_shm_ids);
      ipc_init_proc_interface("sysvipc/shm",
                        "       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime\n",
                        IPC_SHM_IDS, sysvipc_shm_proc_show);
}

/*
 * shm_lock_(check_)down routines are called in the paths where the rw_mutex
 * is held to protect access to the idr tree.
 */
static inline struct shmid_kernel *shm_lock_down(struct ipc_namespace *ns,
                                    int id)
{
      struct kern_ipc_perm *ipcp = ipc_lock_down(&shm_ids(ns), id);

      return container_of(ipcp, struct shmid_kernel, shm_perm);
}

static inline struct shmid_kernel *shm_lock_check_down(
                                    struct ipc_namespace *ns,
                                    int id)
{
      struct kern_ipc_perm *ipcp = ipc_lock_check_down(&shm_ids(ns), id);

      return container_of(ipcp, struct shmid_kernel, shm_perm);
}

/*
 * shm_lock_(check_) routines are called in the paths where the rw_mutex
 * is not held.
 */
static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
{
      struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id);

      return container_of(ipcp, struct shmid_kernel, shm_perm);
}

static inline struct shmid_kernel *shm_lock_check(struct ipc_namespace *ns,
                                    int id)
{
      struct kern_ipc_perm *ipcp = ipc_lock_check(&shm_ids(ns), id);

      return container_of(ipcp, struct shmid_kernel, shm_perm);
}

static inline void shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *s)
{
      ipc_rmid(&shm_ids(ns), &s->shm_perm);
}

static inline int shm_addid(struct ipc_namespace *ns, struct shmid_kernel *shp)
{
      return ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
}



/* This is called by fork, once for every shm attach. */
static void shm_open(struct vm_area_struct *vma)
{
      struct file *file = vma->vm_file;
      struct shm_file_data *sfd = shm_file_data(file);
      struct shmid_kernel *shp;

      shp = shm_lock(sfd->ns, sfd->id);
      BUG_ON(IS_ERR(shp));
      shp->shm_atim = get_seconds();
      shp->shm_lprid = task_tgid_vnr(current);
      shp->shm_nattch++;
      shm_unlock(shp);
}

/*
 * shm_destroy - free the struct shmid_kernel
 *
 * @ns: namespace
 * @shp: struct to free
 *
 * It has to be called with shp and shm_ids.rw_mutex (writer) locked,
 * but returns with shp unlocked and freed.
 */
static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
{
      ns->shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
      shm_rmid(ns, shp);
      shm_unlock(shp);
      if (!is_file_hugepages(shp->shm_file))
            shmem_lock(shp->shm_file, 0, shp->mlock_user);
      else
            user_shm_unlock(shp->shm_file->f_path.dentry->d_inode->i_size,
                                    shp->mlock_user);
      fput (shp->shm_file);
      security_shm_free(shp);
      ipc_rcu_putref(shp);
}

/*
 * remove the attach descriptor vma.
 * free memory for segment if it is marked destroyed.
 * The descriptor has already been removed from the current->mm->mmap list
 * and will later be kfree()d.
 */
static void shm_close(struct vm_area_struct *vma)
{
      struct file * file = vma->vm_file;
      struct shm_file_data *sfd = shm_file_data(file);
      struct shmid_kernel *shp;
      struct ipc_namespace *ns = sfd->ns;

      down_write(&shm_ids(ns).rw_mutex);
      /* remove from the list of attaches of the shm segment */
      shp = shm_lock_down(ns, sfd->id);
      BUG_ON(IS_ERR(shp));
      shp->shm_lprid = task_tgid_vnr(current);
      shp->shm_dtim = get_seconds();
      shp->shm_nattch--;
      if(shp->shm_nattch == 0 &&
         shp->shm_perm.mode & SHM_DEST)
            shm_destroy(ns, shp);
      else
            shm_unlock(shp);
      up_write(&shm_ids(ns).rw_mutex);
}

static int shm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
      struct file *file = vma->vm_file;
      struct shm_file_data *sfd = shm_file_data(file);

      return sfd->vm_ops->fault(vma, vmf);
}

#ifdef CONFIG_NUMA
static int shm_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
{
      struct file *file = vma->vm_file;
      struct shm_file_data *sfd = shm_file_data(file);
      int err = 0;
      if (sfd->vm_ops->set_policy)
            err = sfd->vm_ops->set_policy(vma, new);
      return err;
}

static struct mempolicy *shm_get_policy(struct vm_area_struct *vma,
                              unsigned long addr)
{
      struct file *file = vma->vm_file;
      struct shm_file_data *sfd = shm_file_data(file);
      struct mempolicy *pol = NULL;

      if (sfd->vm_ops->get_policy)
            pol = sfd->vm_ops->get_policy(vma, addr);
      else if (vma->vm_policy)
            pol = vma->vm_policy;
      else
            pol = current->mempolicy;
      return pol;
}
#endif

static int shm_mmap(struct file * file, struct vm_area_struct * vma)
{
      struct shm_file_data *sfd = shm_file_data(file);
      int ret;

      ret = sfd->file->f_op->mmap(sfd->file, vma);
      if (ret != 0)
            return ret;
      sfd->vm_ops = vma->vm_ops;
#ifdef CONFIG_MMU
      BUG_ON(!sfd->vm_ops->fault);
#endif
      vma->vm_ops = &shm_vm_ops;
      shm_open(vma);

      return ret;
}

static int shm_release(struct inode *ino, struct file *file)
{
      struct shm_file_data *sfd = shm_file_data(file);

      put_ipc_ns(sfd->ns);
      shm_file_data(file) = NULL;
      kfree(sfd);
      return 0;
}

static int shm_fsync(struct file *file, struct dentry *dentry, int datasync)
{
      int (*fsync) (struct file *, struct dentry *, int datasync);
      struct shm_file_data *sfd = shm_file_data(file);
      int ret = -EINVAL;

      fsync = sfd->file->f_op->fsync;
      if (fsync)
            ret = fsync(sfd->file, sfd->file->f_path.dentry, datasync);
      return ret;
}

static unsigned long shm_get_unmapped_area(struct file *file,
      unsigned long addr, unsigned long len, unsigned long pgoff,
      unsigned long flags)
{
      struct shm_file_data *sfd = shm_file_data(file);
      return get_unmapped_area(sfd->file, addr, len, pgoff, flags);
}

int is_file_shm_hugepages(struct file *file)
{
      int ret = 0;

      if (file->f_op == &shm_file_operations) {
            struct shm_file_data *sfd;
            sfd = shm_file_data(file);
            ret = is_file_hugepages(sfd->file);
      }
      return ret;
}

static const struct file_operations shm_file_operations = {
      .mmap       = shm_mmap,
      .fsync            = shm_fsync,
      .release    = shm_release,
      .get_unmapped_area      = shm_get_unmapped_area,
};

static struct vm_operations_struct shm_vm_ops = {
      .open = shm_open, /* callback for a new vm-area open */
      .close      = shm_close,      /* callback for when the vm-area is released */
      .fault      = shm_fault,
#if defined(CONFIG_NUMA)
      .set_policy = shm_set_policy,
      .get_policy = shm_get_policy,
#endif
};

/**
 * newseg - Create a new shared memory segment
 * @ns: namespace
 * @params: ptr to the structure that contains key, size and shmflg
 *
 * Called with shm_ids.rw_mutex held as a writer.
 */

static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
{
      key_t key = params->key;
      int shmflg = params->flg;
      size_t size = params->u.size;
      int error;
      struct shmid_kernel *shp;
      int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT;
      struct file * file;
      char name[13];
      int id;

      if (size < SHMMIN || size > ns->shm_ctlmax)
            return -EINVAL;

      if (ns->shm_tot + numpages > ns->shm_ctlall)
            return -ENOSPC;

      shp = ipc_rcu_alloc(sizeof(*shp));
      if (!shp)
            return -ENOMEM;

      shp->shm_perm.key = key;
      shp->shm_perm.mode = (shmflg & S_IRWXUGO);
      shp->mlock_user = NULL;

      shp->shm_perm.security = NULL;
      error = security_shm_alloc(shp);
      if (error) {
            ipc_rcu_putref(shp);
            return error;
      }

      sprintf (name, "SYSV%08x", key);
      if (shmflg & SHM_HUGETLB) {
            /* hugetlb_file_setup takes care of mlock user accounting */
            file = hugetlb_file_setup(name, size);
            shp->mlock_user = current->user;
      } else {
            int acctflag = VM_ACCOUNT;
            /*
             * Do not allow no accounting for OVERCOMMIT_NEVER, even
             * if it's asked for.
             */
            if  ((shmflg & SHM_NORESERVE) &&
                        sysctl_overcommit_memory != OVERCOMMIT_NEVER)
                  acctflag = 0;
            file = shmem_file_setup(name, size, acctflag);
      }
      error = PTR_ERR(file);
      if (IS_ERR(file))
            goto no_file;

      id = shm_addid(ns, shp);
      if (id < 0) {
            error = id;
            goto no_id;
      }

      shp->shm_cprid = task_tgid_vnr(current);
      shp->shm_lprid = 0;
      shp->shm_atim = shp->shm_dtim = 0;
      shp->shm_ctim = get_seconds();
      shp->shm_segsz = size;
      shp->shm_nattch = 0;
      shp->shm_perm.id = shm_buildid(id, shp->shm_perm.seq);
      shp->shm_file = file;
      /*
       * shmid gets reported as "inode#" in /proc/pid/maps.
       * proc-ps tools use this. Changing this will break them.
       */
      file->f_dentry->d_inode->i_ino = shp->shm_perm.id;

      ns->shm_tot += numpages;
      error = shp->shm_perm.id;
      shm_unlock(shp);
      return error;

no_id:
      fput(file);
no_file:
      security_shm_free(shp);
      ipc_rcu_putref(shp);
      return error;
}

/*
 * Called with shm_ids.rw_mutex and ipcp locked.
 */
static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg)
{
      struct shmid_kernel *shp;

      shp = container_of(ipcp, struct shmid_kernel, shm_perm);
      return security_shm_associate(shp, shmflg);
}

/*
 * Called with shm_ids.rw_mutex and ipcp locked.
 */
static inline int shm_more_checks(struct kern_ipc_perm *ipcp,
                        struct ipc_params *params)
{
      struct shmid_kernel *shp;

      shp = container_of(ipcp, struct shmid_kernel, shm_perm);
      if (shp->shm_segsz < params->u.size)
            return -EINVAL;

      return 0;
}

asmlinkage long sys_shmget (key_t key, size_t size, int shmflg)
{
      struct ipc_namespace *ns;
      struct ipc_ops shm_ops;
      struct ipc_params shm_params;

      ns = current->nsproxy->ipc_ns;

      shm_ops.getnew = newseg;
      shm_ops.associate = shm_security;
      shm_ops.more_checks = shm_more_checks;

      shm_params.key = key;
      shm_params.flg = shmflg;
      shm_params.u.size = size;

      return ipcget(ns, &shm_ids(ns), &shm_ops, &shm_params);
}

static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_ds *in, int version)
{
      switch(version) {
      case IPC_64:
            return copy_to_user(buf, in, sizeof(*in));
      case IPC_OLD:
          {
            struct shmid_ds out;

            ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
            out.shm_segsz     = in->shm_segsz;
            out.shm_atime     = in->shm_atime;
            out.shm_dtime     = in->shm_dtime;
            out.shm_ctime     = in->shm_ctime;
            out.shm_cpid      = in->shm_cpid;
            out.shm_lpid      = in->shm_lpid;
            out.shm_nattch    = in->shm_nattch;

            return copy_to_user(buf, &out, sizeof(out));
          }
      default:
            return -EINVAL;
      }
}

struct shm_setbuf {
      uid_t uid;
      gid_t gid;
      mode_t      mode;
};    

static inline unsigned long copy_shmid_from_user(struct shm_setbuf *out, void __user *buf, int version)
{
      switch(version) {
      case IPC_64:
          {
            struct shmid64_ds tbuf;

            if (copy_from_user(&tbuf, buf, sizeof(tbuf)))
                  return -EFAULT;

            out->uid    = tbuf.shm_perm.uid;
            out->gid    = tbuf.shm_perm.gid;
            out->mode   = tbuf.shm_perm.mode;

            return 0;
          }
      case IPC_OLD:
          {
            struct shmid_ds tbuf_old;

            if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
                  return -EFAULT;

            out->uid    = tbuf_old.shm_perm.uid;
            out->gid    = tbuf_old.shm_perm.gid;
            out->mode   = tbuf_old.shm_perm.mode;

            return 0;
          }
      default:
            return -EINVAL;
      }
}

static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminfo64 *in, int version)
{
      switch(version) {
      case IPC_64:
            return copy_to_user(buf, in, sizeof(*in));
      case IPC_OLD:
          {
            struct shminfo out;

            if(in->shmmax > INT_MAX)
                  out.shmmax = INT_MAX;
            else
                  out.shmmax = (int)in->shmmax;

            out.shmmin  = in->shmmin;
            out.shmmni  = in->shmmni;
            out.shmseg  = in->shmseg;
            out.shmall  = in->shmall; 

            return copy_to_user(buf, &out, sizeof(out));
          }
      default:
            return -EINVAL;
      }
}

/*
 * Called with shm_ids.rw_mutex held as a reader
 */
static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss,
            unsigned long *swp)
{
      int next_id;
      int total, in_use;

      *rss = 0;
      *swp = 0;

      in_use = shm_ids(ns).in_use;

      for (total = 0, next_id = 0; total < in_use; next_id++) {
            struct shmid_kernel *shp;
            struct inode *inode;

            shp = idr_find(&shm_ids(ns).ipcs_idr, next_id);
            if (shp == NULL)
                  continue;

            inode = shp->shm_file->f_path.dentry->d_inode;

            if (is_file_hugepages(shp->shm_file)) {
                  struct address_space *mapping = inode->i_mapping;
                  *rss += (HPAGE_SIZE/PAGE_SIZE)*mapping->nrpages;
            } else {
                  struct shmem_inode_info *info = SHMEM_I(inode);
                  spin_lock(&info->lock);
                  *rss += inode->i_mapping->nrpages;
                  *swp += info->swapped;
                  spin_unlock(&info->lock);
            }

            total++;
      }
}

asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf)
{
      struct shm_setbuf setbuf;
      struct shmid_kernel *shp;
      int err, version;
      struct ipc_namespace *ns;

      if (cmd < 0 || shmid < 0) {
            err = -EINVAL;
            goto out;
      }

      version = ipc_parse_version(&cmd);
      ns = current->nsproxy->ipc_ns;

      switch (cmd) { /* replace with proc interface ? */
      case IPC_INFO:
      {
            struct shminfo64 shminfo;

            err = security_shm_shmctl(NULL, cmd);
            if (err)
                  return err;

            memset(&shminfo,0,sizeof(shminfo));
            shminfo.shmmni = shminfo.shmseg = ns->shm_ctlmni;
            shminfo.shmmax = ns->shm_ctlmax;
            shminfo.shmall = ns->shm_ctlall;

            shminfo.shmmin = SHMMIN;
            if(copy_shminfo_to_user (buf, &shminfo, version))
                  return -EFAULT;

            down_read(&shm_ids(ns).rw_mutex);
            err = ipc_get_maxid(&shm_ids(ns));
            up_read(&shm_ids(ns).rw_mutex);

            if(err<0)
                  err = 0;
            goto out;
      }
      case SHM_INFO:
      {
            struct shm_info shm_info;

            err = security_shm_shmctl(NULL, cmd);
            if (err)
                  return err;

            memset(&shm_info,0,sizeof(shm_info));
            down_read(&shm_ids(ns).rw_mutex);
            shm_info.used_ids = shm_ids(ns).in_use;
            shm_get_stat (ns, &shm_info.shm_rss, &shm_info.shm_swp);
            shm_info.shm_tot = ns->shm_tot;
            shm_info.swap_attempts = 0;
            shm_info.swap_successes = 0;
            err = ipc_get_maxid(&shm_ids(ns));
            up_read(&shm_ids(ns).rw_mutex);
            if(copy_to_user (buf, &shm_info, sizeof(shm_info))) {
                  err = -EFAULT;
                  goto out;
            }

            err = err < 0 ? 0 : err;
            goto out;
      }
      case SHM_STAT:
      case IPC_STAT:
      {
            struct shmid64_ds tbuf;
            int result;

            if (!buf) {
                  err = -EFAULT;
                  goto out;
            }

            if (cmd == SHM_STAT) {
                  shp = shm_lock(ns, shmid);
                  if (IS_ERR(shp)) {
                        err = PTR_ERR(shp);
                        goto out;
                  }
                  result = shp->shm_perm.id;
            } else {
                  shp = shm_lock_check(ns, shmid);
                  if (IS_ERR(shp)) {
                        err = PTR_ERR(shp);
                        goto out;
                  }
                  result = 0;
            }
            err=-EACCES;
            if (ipcperms (&shp->shm_perm, S_IRUGO))
                  goto out_unlock;
            err = security_shm_shmctl(shp, cmd);
            if (err)
                  goto out_unlock;
            memset(&tbuf, 0, sizeof(tbuf));
            kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
            tbuf.shm_segsz    = shp->shm_segsz;
            tbuf.shm_atime    = shp->shm_atim;
            tbuf.shm_dtime    = shp->shm_dtim;
            tbuf.shm_ctime    = shp->shm_ctim;
            tbuf.shm_cpid     = shp->shm_cprid;
            tbuf.shm_lpid     = shp->shm_lprid;
            tbuf.shm_nattch   = shp->shm_nattch;
            shm_unlock(shp);
            if(copy_shmid_to_user (buf, &tbuf, version))
                  err = -EFAULT;
            else
                  err = result;
            goto out;
      }
      case SHM_LOCK:
      case SHM_UNLOCK:
      {
            shp = shm_lock_check(ns, shmid);
            if (IS_ERR(shp)) {
                  err = PTR_ERR(shp);
                  goto out;
            }

            err = audit_ipc_obj(&(shp->shm_perm));
            if (err)
                  goto out_unlock;

            if (!capable(CAP_IPC_LOCK)) {
                  err = -EPERM;
                  if (current->euid != shp->shm_perm.uid &&
                      current->euid != shp->shm_perm.cuid)
                        goto out_unlock;
                  if (cmd == SHM_LOCK &&
                      !current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur)
                        goto out_unlock;
            }

            err = security_shm_shmctl(shp, cmd);
            if (err)
                  goto out_unlock;
            
            if(cmd==SHM_LOCK) {
                  struct user_struct * user = current->user;
                  if (!is_file_hugepages(shp->shm_file)) {
                        err = shmem_lock(shp->shm_file, 1, user);
                        if (!err && !(shp->shm_perm.mode & SHM_LOCKED)){
                              shp->shm_perm.mode |= SHM_LOCKED;
                              shp->mlock_user = user;
                        }
                  }
            } else if (!is_file_hugepages(shp->shm_file)) {
                  shmem_lock(shp->shm_file, 0, shp->mlock_user);
                  shp->shm_perm.mode &= ~SHM_LOCKED;
                  shp->mlock_user = NULL;
            }
            shm_unlock(shp);
            goto out;
      }
      case IPC_RMID:
      {
            /*
             *    We cannot simply remove the file. The SVID states
             *    that the block remains until the last person
             *    detaches from it, then is deleted. A shmat() on
             *    an RMID segment is legal in older Linux and if 
             *    we change it apps break...
             *
             *    Instead we set a destroyed flag, and then blow
             *    the name away when the usage hits zero.
             */
            down_write(&shm_ids(ns).rw_mutex);
            shp = shm_lock_check_down(ns, shmid);
            if (IS_ERR(shp)) {
                  err = PTR_ERR(shp);
                  goto out_up;
            }

            err = audit_ipc_obj(&(shp->shm_perm));
            if (err)
                  goto out_unlock_up;

            if (current->euid != shp->shm_perm.uid &&
                current->euid != shp->shm_perm.cuid && 
                !capable(CAP_SYS_ADMIN)) {
                  err=-EPERM;
                  goto out_unlock_up;
            }

            err = security_shm_shmctl(shp, cmd);
            if (err)
                  goto out_unlock_up;

            do_shm_rmid(ns, shp);
            up_write(&shm_ids(ns).rw_mutex);
            goto out;
      }

      case IPC_SET:
      {
            if (!buf) {
                  err = -EFAULT;
                  goto out;
            }

            if (copy_shmid_from_user (&setbuf, buf, version)) {
                  err = -EFAULT;
                  goto out;
            }
            down_write(&shm_ids(ns).rw_mutex);
            shp = shm_lock_check_down(ns, shmid);
            if (IS_ERR(shp)) {
                  err = PTR_ERR(shp);
                  goto out_up;
            }
            err = audit_ipc_obj(&(shp->shm_perm));
            if (err)
                  goto out_unlock_up;
            err = audit_ipc_set_perm(0, setbuf.uid, setbuf.gid, setbuf.mode);
            if (err)
                  goto out_unlock_up;
            err=-EPERM;
            if (current->euid != shp->shm_perm.uid &&
                current->euid != shp->shm_perm.cuid && 
                !capable(CAP_SYS_ADMIN)) {
                  goto out_unlock_up;
            }

            err = security_shm_shmctl(shp, cmd);
            if (err)
                  goto out_unlock_up;
            
            shp->shm_perm.uid = setbuf.uid;
            shp->shm_perm.gid = setbuf.gid;
            shp->shm_perm.mode = (shp->shm_perm.mode & ~S_IRWXUGO)
                  | (setbuf.mode & S_IRWXUGO);
            shp->shm_ctim = get_seconds();
            break;
      }

      default:
            err = -EINVAL;
            goto out;
      }

      err = 0;
out_unlock_up:
      shm_unlock(shp);
out_up:
      up_write(&shm_ids(ns).rw_mutex);
      goto out;
out_unlock:
      shm_unlock(shp);
out:
      return err;
}

/*
 * Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists.
 *
 * NOTE! Despite the name, this is NOT a direct system call entrypoint. The
 * "raddr" thing points to kernel space, and there has to be a wrapper around
 * this.
 */
long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
{
      struct shmid_kernel *shp;
      unsigned long addr;
      unsigned long size;
      struct file * file;
      int    err;
      unsigned long flags;
      unsigned long prot;
      int acc_mode;
      unsigned long user_addr;
      struct ipc_namespace *ns;
      struct shm_file_data *sfd;
      struct path path;
      mode_t f_mode;

      err = -EINVAL;
      if (shmid < 0)
            goto out;
      else if ((addr = (ulong)shmaddr)) {
            if (addr & (SHMLBA-1)) {
                  if (shmflg & SHM_RND)
                        addr &= ~(SHMLBA-1);       /* round down */
                  else
#ifndef __ARCH_FORCE_SHMLBA
                        if (addr & ~PAGE_MASK)
#endif
                              goto out;
            }
            flags = MAP_SHARED | MAP_FIXED;
      } else {
            if ((shmflg & SHM_REMAP))
                  goto out;

            flags = MAP_SHARED;
      }

      if (shmflg & SHM_RDONLY) {
            prot = PROT_READ;
            acc_mode = S_IRUGO;
            f_mode = FMODE_READ;
      } else {
            prot = PROT_READ | PROT_WRITE;
            acc_mode = S_IRUGO | S_IWUGO;
            f_mode = FMODE_READ | FMODE_WRITE;
      }
      if (shmflg & SHM_EXEC) {
            prot |= PROT_EXEC;
            acc_mode |= S_IXUGO;
      }

      /*
       * We cannot rely on the fs check since SYSV IPC does have an
       * additional creator id...
       */
      ns = current->nsproxy->ipc_ns;
      shp = shm_lock_check(ns, shmid);
      if (IS_ERR(shp)) {
            err = PTR_ERR(shp);
            goto out;
      }

      err = -EACCES;
      if (ipcperms(&shp->shm_perm, acc_mode))
            goto out_unlock;

      err = security_shm_shmat(shp, shmaddr, shmflg);
      if (err)
            goto out_unlock;

      path.dentry = dget(shp->shm_file->f_path.dentry);
      path.mnt    = shp->shm_file->f_path.mnt;
      shp->shm_nattch++;
      size = i_size_read(path.dentry->d_inode);
      shm_unlock(shp);

      err = -ENOMEM;
      sfd = kzalloc(sizeof(*sfd), GFP_KERNEL);
      if (!sfd)
            goto out_put_dentry;

      err = -ENOMEM;

      file = alloc_file(path.mnt, path.dentry, f_mode, &shm_file_operations);
      if (!file)
            goto out_free;

      file->private_data = sfd;
      file->f_mapping = shp->shm_file->f_mapping;
      sfd->id = shp->shm_perm.id;
      sfd->ns = get_ipc_ns(ns);
      sfd->file = shp->shm_file;
      sfd->vm_ops = NULL;

      down_write(&current->mm->mmap_sem);
      if (addr && !(shmflg & SHM_REMAP)) {
            err = -EINVAL;
            if (find_vma_intersection(current->mm, addr, addr + size))
                  goto invalid;
            /*
             * If shm segment goes below stack, make sure there is some
             * space left for the stack to grow (at least 4 pages).
             */
            if (addr < current->mm->start_stack &&
                addr > current->mm->start_stack - size - PAGE_SIZE * 5)
                  goto invalid;
      }
            
      user_addr = do_mmap (file, addr, size, prot, flags, 0);
      *raddr = user_addr;
      err = 0;
      if (IS_ERR_VALUE(user_addr))
            err = (long)user_addr;
invalid:
      up_write(&current->mm->mmap_sem);

      fput(file);

out_nattch:
      down_write(&shm_ids(ns).rw_mutex);
      shp = shm_lock_down(ns, shmid);
      BUG_ON(IS_ERR(shp));
      shp->shm_nattch--;
      if(shp->shm_nattch == 0 &&
         shp->shm_perm.mode & SHM_DEST)
            shm_destroy(ns, shp);
      else
            shm_unlock(shp);
      up_write(&shm_ids(ns).rw_mutex);

out:
      return err;

out_unlock:
      shm_unlock(shp);
      goto out;

out_free:
      kfree(sfd);
out_put_dentry:
      dput(path.dentry);
      goto out_nattch;
}

asmlinkage long sys_shmat(int shmid, char __user *shmaddr, int shmflg)
{
      unsigned long ret;
      long err;

      err = do_shmat(shmid, shmaddr, shmflg, &ret);
      if (err)
            return err;
      force_successful_syscall_return();
      return (long)ret;
}

/*
 * detach and kill segment if marked destroyed.
 * The work is done in shm_close.
 */
asmlinkage long sys_shmdt(char __user *shmaddr)
{
      struct mm_struct *mm = current->mm;
      struct vm_area_struct *vma, *next;
      unsigned long addr = (unsigned long)shmaddr;
      loff_t size = 0;
      int retval = -EINVAL;

      if (addr & ~PAGE_MASK)
            return retval;

      down_write(&mm->mmap_sem);

      /*
       * This function tries to be smart and unmap shm segments that
       * were modified by partial mlock or munmap calls:
       * - It first determines the size of the shm segment that should be
       *   unmapped: It searches for a vma that is backed by shm and that
       *   started at address shmaddr. It records it's size and then unmaps
       *   it.
       * - Then it unmaps all shm vmas that started at shmaddr and that
       *   are within the initially determined size.
       * Errors from do_munmap are ignored: the function only fails if
       * it's called with invalid parameters or if it's called to unmap
       * a part of a vma. Both calls in this function are for full vmas,
       * the parameters are directly copied from the vma itself and always
       * valid - therefore do_munmap cannot fail. (famous last words?)
       */
      /*
       * If it had been mremap()'d, the starting address would not
       * match the usual checks anyway. So assume all vma's are
       * above the starting address given.
       */
      vma = find_vma(mm, addr);

      while (vma) {
            next = vma->vm_next;

            /*
             * Check if the starting address would match, i.e. it's
             * a fragment created by mprotect() and/or munmap(), or it
             * otherwise it starts at this address with no hassles.
             */
            if ((vma->vm_ops == &shm_vm_ops) &&
                  (vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) {


                  size = vma->vm_file->f_path.dentry->d_inode->i_size;
                  do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
                  /*
                   * We discovered the size of the shm segment, so
                   * break out of here and fall through to the next
                   * loop that uses the size information to stop
                   * searching for matching vma's.
                   */
                  retval = 0;
                  vma = next;
                  break;
            }
            vma = next;
      }

      /*
       * We need look no further than the maximum address a fragment
       * could possibly have landed at. Also cast things to loff_t to
       * prevent overflows and make comparisions vs. equal-width types.
       */
      size = PAGE_ALIGN(size);
      while (vma && (loff_t)(vma->vm_end - addr) <= size) {
            next = vma->vm_next;

            /* finding a matching vma now does not alter retval */
            if ((vma->vm_ops == &shm_vm_ops) &&
                  (vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff)

                  do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
            vma = next;
      }

      up_write(&mm->mmap_sem);
      return retval;
}

#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it)
{
      struct shmid_kernel *shp = it;
      char *format;

#define SMALL_STRING "%10d %10d  %4o %10u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
#define BIG_STRING   "%10d %10d  %4o %21u %5u %5u  %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"

      if (sizeof(size_t) <= sizeof(int))
            format = SMALL_STRING;
      else
            format = BIG_STRING;
      return seq_printf(s, format,
                    shp->shm_perm.key,
                    shp->shm_perm.id,
                    shp->shm_perm.mode,
                    shp->shm_segsz,
                    shp->shm_cprid,
                    shp->shm_lprid,
                    shp->shm_nattch,
                    shp->shm_perm.uid,
                    shp->shm_perm.gid,
                    shp->shm_perm.cuid,
                    shp->shm_perm.cgid,
                    shp->shm_atim,
                    shp->shm_dtim,
                    shp->shm_ctim);
}
#endif

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