// SPDX-License-Identifier: GPL-2.0

  /*
   * 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>

   *
   * Better ipc lock (kern_ipc_perm.lock) handling
   * Davidlohr Bueso <davidlohr.bueso@hp.com>, June 2013.

   */

  #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 <linux/ipc_namespace.h>

  #include <linux/rhashtable.h>

  #include <linux/uaccess.h>

  
  #include "util.h"

  struct shmid_kernel /* private to the kernel */
  {
  	struct kern_ipc_perm	shm_perm;
  	struct file		*shm_file;
  	unsigned long		shm_nattch;
  	unsigned long		shm_segsz;
  	time64_t		shm_atim;
  	time64_t		shm_dtim;
  	time64_t		shm_ctim;

  	struct pid		*shm_cprid;
  	struct pid		*shm_lprid;

  	struct user_struct	*mlock_user;
  
  	/* The task created the shm object.  NULL if the task is dead. */
  	struct task_struct	*shm_creator;
  	struct list_head	shm_clist;	/* list by creator */
  } __randomize_layout;
  
  /* shm_mode upper byte flags */
  #define SHM_DEST	01000	/* segment will be destroyed on last detach */
  #define SHM_LOCKED	02000   /* segment will not be swapped */

  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 const struct vm_operations_struct shm_vm_ops;

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

  #define shm_unlock(shp)			\
  	ipc_unlock(&(shp)->shm_perm)

  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

  void shm_init_ns(struct ipc_namespace *ns)

  {

  	ns->shm_ctlmax = SHMMAX;
  	ns->shm_ctlall = SHMALL;
  	ns->shm_ctlmni = SHMMNI;

  	ns->shm_rmid_forced = 0;

  	ns->shm_tot = 0;

  	ipc_init_ids(&shm_ids(ns));

  }

  /*

   * Called with shm_ids.rwsem (writer) and the shp structure locked.
   * Only shm_ids.rwsem remains locked on exit.

   */

  static void do_shm_rmid(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)

  {

  	struct shmid_kernel *shp;

  	shp = container_of(ipcp, struct shmid_kernel, shm_perm);

  	if (shp->shm_nattch) {

  		shp->shm_perm.mode |= SHM_DEST;
  		/* Do not find it any more */

  		ipc_set_key_private(&shm_ids(ns), &shp->shm_perm);

  		shm_unlock(shp);
  	} else
  		shm_destroy(ns, shp);
  }

  #ifdef CONFIG_IPC_NS

  void shm_exit_ns(struct ipc_namespace *ns)
  {

  	free_ipcs(ns, &shm_ids(ns), do_shm_rmid);

  	idr_destroy(&ns->ids[IPC_SHM_IDS].ipcs_idr);

  	rhashtable_destroy(&ns->ids[IPC_SHM_IDS].key_ht);

  }

  #endif

  static int __init ipc_ns_init(void)

  {

  	shm_init_ns(&init_ipc_ns);
  	return 0;

  }
  
  pure_initcall(ipc_ns_init);

  void __init shm_init(void)

  {

  	ipc_init_proc_interface("sysvipc/shm",

  #if BITS_PER_LONG <= 32
  				"       key      shmid perms       size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime        rss       swap
  ",
  #else
  				"       key      shmid perms                  size  cpid  lpid nattch   uid   gid  cuid  cgid      atime      dtime      ctime                   rss                  swap
  ",
  #endif

  				IPC_SHM_IDS, sysvipc_shm_proc_show);

  }

  static inline struct shmid_kernel *shm_obtain_object(struct ipc_namespace *ns, int id)
  {

  	struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&shm_ids(ns), id);

  
  	if (IS_ERR(ipcp))
  		return ERR_CAST(ipcp);
  
  	return container_of(ipcp, struct shmid_kernel, shm_perm);
  }
  
  static inline struct shmid_kernel *shm_obtain_object_check(struct ipc_namespace *ns, int id)
  {
  	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&shm_ids(ns), id);
  
  	if (IS_ERR(ipcp))
  		return ERR_CAST(ipcp);
  
  	return container_of(ipcp, struct shmid_kernel, shm_perm);
  }

  /*

   * shm_lock_(check_) routines are called in the paths where the rwsem

   * is not necessarily held.

   */

  static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)

  {

  	struct kern_ipc_perm *ipcp;

  	rcu_read_lock();
  	ipcp = ipc_obtain_object_idr(&shm_ids(ns), id);
  	if (IS_ERR(ipcp))
  		goto err;
  
  	ipc_lock_object(ipcp);
  	/*
  	 * ipc_rmid() may have already freed the ID while ipc_lock_object()
  	 * was spinning: here verify that the structure is still valid.
  	 * Upon races with RMID, return -EIDRM, thus indicating that
  	 * the ID points to a removed identifier.
  	 */
  	if (ipc_valid_object(ipcp)) {
  		/* return a locked ipc object upon success */
  		return container_of(ipcp, struct shmid_kernel, shm_perm);
  	}
  
  	ipc_unlock_object(ipcp);

  	ipcp = ERR_PTR(-EIDRM);

  err:
  	rcu_read_unlock();

  	/*

  	 * Callers of shm_lock() must validate the status of the returned ipc

  	 * object pointer and error out as appropriate.

  	 */

  	return ERR_CAST(ipcp);

  }

  static inline void shm_lock_by_ptr(struct shmid_kernel *ipcp)
  {
  	rcu_read_lock();

  	ipc_lock_object(&ipcp->shm_perm);

  }

  static void shm_rcu_free(struct rcu_head *head)
  {

  	struct kern_ipc_perm *ptr = container_of(head, struct kern_ipc_perm,
  							rcu);
  	struct shmid_kernel *shp = container_of(ptr, struct shmid_kernel,
  							shm_perm);

  	security_shm_free(&shp->shm_perm);

  	kvfree(shp);

  }

  static inline void shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *s)

  {

  	list_del(&s->shm_clist);

  	ipc_rmid(&shm_ids(ns), &s->shm_perm);

  }

  static int __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);

  
  	if (IS_ERR(shp))
  		return PTR_ERR(shp);

  	if (shp->shm_file != sfd->file) {
  		/* ID was reused */
  		shm_unlock(shp);
  		return -EINVAL;
  	}

  	shp->shm_atim = ktime_get_real_seconds();

  	ipc_update_pid(&shp->shm_lprid, task_tgid(current));

  	shp->shm_nattch++;
  	shm_unlock(shp);

  	return 0;
  }
  
  /* This is called by fork, once for every shm attach. */
  static void shm_open(struct vm_area_struct *vma)
  {
  	int err = __shm_open(vma);
  	/*
  	 * We raced in the idr lookup or with shm_destroy().
  	 * Either way, the ID is busted.
  	 */
  	WARN_ON_ONCE(err);

  }

  /*
   * shm_destroy - free the struct shmid_kernel
   *

   * @ns: namespace

   * @shp: struct to free
   *

   * It has to be called with shp and shm_ids.rwsem (writer) locked,

   * but returns with shp unlocked and freed.
   */

  static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)

  {

  	struct file *shm_file;
  
  	shm_file = shp->shm_file;
  	shp->shm_file = NULL;

  	ns->shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;

  	shm_rmid(ns, shp);

  	shm_unlock(shp);

  	if (!is_file_hugepages(shm_file))
  		shmem_lock(shm_file, 0, shp->mlock_user);

  	else if (shp->mlock_user)

  		user_shm_unlock(i_size_read(file_inode(shm_file)),
  				shp->mlock_user);

  	fput(shm_file);

  	ipc_update_pid(&shp->shm_cprid, NULL);
  	ipc_update_pid(&shp->shm_lprid, NULL);

  	ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);

  }
  
  /*

   * shm_may_destroy - identifies whether shm segment should be destroyed now
   *
   * Returns true if and only if there are no active users of the segment and
   * one of the following is true:
   *
   * 1) shmctl(id, IPC_RMID, NULL) was called for this shp
   *
   * 2) sysctl kernel.shm_rmid_forced is set to 1.
   */
  static bool shm_may_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
  {
  	return (shp->shm_nattch == 0) &&
  	       (ns->shm_rmid_forced ||
  		(shp->shm_perm.mode & SHM_DEST));
  }
  
  /*

   * 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).rwsem);

  	/* remove from the list of attaches of the shm segment */

  	shp = shm_lock(ns, sfd->id);

  
  	/*
  	 * We raced in the idr lookup or with shm_destroy().
  	 * Either way, the ID is busted.
  	 */
  	if (WARN_ON_ONCE(IS_ERR(shp)))
  		goto done; /* no-op */

  	ipc_update_pid(&shp->shm_lprid, task_tgid(current));

  	shp->shm_dtim = ktime_get_real_seconds();

  	shp->shm_nattch--;

  	if (shm_may_destroy(ns, shp))
  		shm_destroy(ns, shp);
  	else
  		shm_unlock(shp);

  done:

  	up_write(&shm_ids(ns).rwsem);

  }

  /* Called with ns->shm_ids(ns).rwsem locked */

  static int shm_try_destroy_orphaned(int id, void *p, void *data)
  {
  	struct ipc_namespace *ns = data;

  	struct kern_ipc_perm *ipcp = p;
  	struct shmid_kernel *shp = container_of(ipcp, struct shmid_kernel, shm_perm);

  
  	/*
  	 * We want to destroy segments without users and with already
  	 * exit'ed originating process.

  	 *

  	 * As shp->* are changed under rwsem, it's safe to skip shp locking.

  	 */

  	if (shp->shm_creator != NULL)

  		return 0;

  	if (shm_may_destroy(ns, shp)) {
  		shm_lock_by_ptr(shp);

  		shm_destroy(ns, shp);

  	}

  	return 0;
  }
  
  void shm_destroy_orphaned(struct ipc_namespace *ns)
  {

  	down_write(&shm_ids(ns).rwsem);

  	if (shm_ids(ns).in_use)

  		idr_for_each(&shm_ids(ns).ipcs_idr, &shm_try_destroy_orphaned, ns);

  	up_write(&shm_ids(ns).rwsem);

  }

  /* Locking assumes this will only be called with task == current */

  void exit_shm(struct task_struct *task)
  {

  	struct ipc_namespace *ns = task->nsproxy->ipc_ns;

  	struct shmid_kernel *shp, *n;

  	if (list_empty(&task->sysvshm.shm_clist))
  		return;
  
  	/*
  	 * If kernel.shm_rmid_forced is not set then only keep track of
  	 * which shmids are orphaned, so that a later set of the sysctl
  	 * can clean them up.
  	 */
  	if (!ns->shm_rmid_forced) {
  		down_read(&shm_ids(ns).rwsem);
  		list_for_each_entry(shp, &task->sysvshm.shm_clist, shm_clist)
  			shp->shm_creator = NULL;
  		/*
  		 * Only under read lock but we are only called on current
  		 * so no entry on the list will be shared.
  		 */
  		list_del(&task->sysvshm.shm_clist);
  		up_read(&shm_ids(ns).rwsem);

  		return;

  	}

  	/*
  	 * Destroy all already created segments, that were not yet mapped,
  	 * and mark any mapped as orphan to cover the sysctl toggling.
  	 * Destroy is skipped if shm_may_destroy() returns false.
  	 */

  	down_write(&shm_ids(ns).rwsem);

  	list_for_each_entry_safe(shp, n, &task->sysvshm.shm_clist, shm_clist) {
  		shp->shm_creator = NULL;
  
  		if (shm_may_destroy(ns, shp)) {
  			shm_lock_by_ptr(shp);
  			shm_destroy(ns, shp);
  		}
  	}
  
  	/* Remove the list head from any segments still attached. */

  	list_del(&task->sysvshm.shm_clist);

  	up_write(&shm_ids(ns).rwsem);

  }

  static vm_fault_t shm_fault(struct vm_fault *vmf)

  {

  	struct file *file = vmf->vma->vm_file;

  	struct shm_file_data *sfd = shm_file_data(file);

  	return sfd->vm_ops->fault(vmf);

  }

  static int shm_split(struct vm_area_struct *vma, unsigned long addr)
  {
  	struct file *file = vma->vm_file;
  	struct shm_file_data *sfd = shm_file_data(file);

  	if (sfd->vm_ops->split)

  		return sfd->vm_ops->split(vma, addr);
  
  	return 0;
  }

  static unsigned long shm_pagesize(struct vm_area_struct *vma)
  {
  	struct file *file = vma->vm_file;
  	struct shm_file_data *sfd = shm_file_data(file);
  
  	if (sfd->vm_ops->pagesize)
  		return sfd->vm_ops->pagesize(vma);
  
  	return PAGE_SIZE;
  }

  #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;

  	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;

  	/*

  	 * In case of remap_file_pages() emulation, the file can represent an
  	 * IPC ID that was removed, and possibly even reused by another shm
  	 * segment already.  Propagate this case as an error to caller.

  	 */

  	ret = __shm_open(vma);

  	if (ret)
  		return ret;

  	ret = call_mmap(sfd->file, vma);

  	if (ret) {
  		shm_close(vma);

  		return ret;

  	}

  	sfd->vm_ops = vma->vm_ops;

  #ifdef CONFIG_MMU

  	WARN_ON(!sfd->vm_ops->fault);

  #endif

  	vma->vm_ops = &shm_vm_ops;

  	return 0;

  }

  static int shm_release(struct inode *ino, struct file *file)
  {

  	struct shm_file_data *sfd = shm_file_data(file);

  	put_ipc_ns(sfd->ns);

  	fput(sfd->file);

  	shm_file_data(file) = NULL;
  	kfree(sfd);

  	return 0;
  }

  static int shm_fsync(struct file *file, loff_t start, loff_t end, int datasync)

  {

  	struct shm_file_data *sfd = shm_file_data(file);

  	if (!sfd->file->f_op->fsync)
  		return -EINVAL;

  	return sfd->file->f_op->fsync(sfd->file, start, end, datasync);

  }

  static long shm_fallocate(struct file *file, int mode, loff_t offset,
  			  loff_t len)
  {
  	struct shm_file_data *sfd = shm_file_data(file);
  
  	if (!sfd->file->f_op->fallocate)
  		return -EOPNOTSUPP;
  	return sfd->file->f_op->fallocate(file, mode, offset, len);
  }

  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 sfd->file->f_op->get_unmapped_area(sfd->file, addr, len,
  						pgoff, flags);

  }

  static const struct file_operations shm_file_operations = {

  	.mmap		= shm_mmap,

  	.fsync		= shm_fsync,

  	.release	= shm_release,

  	.get_unmapped_area	= shm_get_unmapped_area,

  	.llseek		= noop_llseek,

  	.fallocate	= shm_fallocate,

  };

  /*
   * shm_file_operations_huge is now identical to shm_file_operations,
   * but we keep it distinct for the sake of is_file_shm_hugepages().
   */

  static const struct file_operations shm_file_operations_huge = {
  	.mmap		= shm_mmap,
  	.fsync		= shm_fsync,
  	.release	= shm_release,

  	.get_unmapped_area	= shm_get_unmapped_area,

  	.llseek		= noop_llseek,

  	.fallocate	= shm_fallocate,

  };

  bool is_file_shm_hugepages(struct file *file)

  {
  	return file->f_op == &shm_file_operations_huge;
  }

  static const 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,

  	.split	= shm_split,

  	.pagesize = shm_pagesize,

  #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.rwsem 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;

  	size_t numpages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;

  	struct file *file;

  	char name[13];

  	vm_flags_t acctflag = 0;

  	if (size < SHMMIN || size > ns->shm_ctlmax)

  		return -EINVAL;

  	if (numpages << PAGE_SHIFT < size)
  		return -ENOSPC;

  	if (ns->shm_tot + numpages < ns->shm_tot ||
  			ns->shm_tot + numpages > ns->shm_ctlall)

  		return -ENOSPC;

  	shp = kvmalloc(sizeof(*shp), GFP_KERNEL);
  	if (unlikely(!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->shm_perm);

  	if (error) {

  		kvfree(shp);

  		return error;
  	}

  	sprintf(name, "SYSV%08x", key);

  	if (shmflg & SHM_HUGETLB) {

  		struct hstate *hs;

  		size_t hugesize;

  		hs = hstate_sizelog((shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);

  		if (!hs) {
  			error = -EINVAL;
  			goto no_file;
  		}
  		hugesize = ALIGN(size, huge_page_size(hs));

  		/* hugetlb_file_setup applies strict accounting */
  		if (shmflg & SHM_NORESERVE)
  			acctflag = VM_NORESERVE;

  		file = hugetlb_file_setup(name, hugesize, acctflag,

  				  &shp->mlock_user, HUGETLB_SHMFS_INODE,
  				(shmflg >> SHM_HUGE_SHIFT) & SHM_HUGE_MASK);

  	} else {

  		/*
  		 * Do not allow no accounting for OVERCOMMIT_NEVER, even

  		 * if it's asked for.

  		 */
  		if  ((shmflg & SHM_NORESERVE) &&
  				sysctl_overcommit_memory != OVERCOMMIT_NEVER)

  			acctflag = VM_NORESERVE;

  		file = shmem_kernel_file_setup(name, size, acctflag);

  	}
  	error = PTR_ERR(file);
  	if (IS_ERR(file))
  		goto no_file;

  	shp->shm_cprid = get_pid(task_tgid(current));
  	shp->shm_lprid = NULL;

  	shp->shm_atim = shp->shm_dtim = 0;

  	shp->shm_ctim = ktime_get_real_seconds();

  	shp->shm_segsz = size;
  	shp->shm_nattch = 0;

  	shp->shm_file = file;

  	shp->shm_creator = current;

  	/* ipc_addid() locks shp upon success. */

  	error = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
  	if (error < 0)

  		goto no_id;

  	list_add(&shp->shm_clist, &current->sysvshm.shm_clist);

  	/*
  	 * shmid gets reported as "inode#" in /proc/pid/maps.
  	 * proc-ps tools use this. Changing this will break them.
  	 */

  	file_inode(file)->i_ino = shp->shm_perm.id;

  	ns->shm_tot += numpages;

  	error = shp->shm_perm.id;

  	ipc_unlock_object(&shp->shm_perm);

  	rcu_read_unlock();

  	return error;

  
  no_id:

  	ipc_update_pid(&shp->shm_cprid, NULL);
  	ipc_update_pid(&shp->shm_lprid, NULL);

  	if (is_file_hugepages(file) && shp->mlock_user)

  		user_shm_unlock(size, shp->mlock_user);

  	fput(file);

  	ipc_rcu_putref(&shp->shm_perm, shm_rcu_free);
  	return error;

  no_file:

  	call_rcu(&shp->shm_perm.rcu, shm_rcu_free);

  	return error;
  }

  /*

   * Called with shm_ids.rwsem 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;
  }

  long ksys_shmget(key_t key, size_t size, int shmflg)

  {

  	struct ipc_namespace *ns;

  	static const struct ipc_ops shm_ops = {
  		.getnew = newseg,

  		.associate = security_shm_associate,

  		.more_checks = shm_more_checks,
  	};

  	struct ipc_params shm_params;

  
  	ns = current->nsproxy->ipc_ns;

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

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

  }

  SYSCALL_DEFINE3(shmget, key_t, key, size_t, size, int, shmflg)
  {
  	return ksys_shmget(key, size, shmflg);
  }

  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;

  		memset(&out, 0, sizeof(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;
  	}
  }

  static inline unsigned long
  copy_shmid_from_user(struct shmid64_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 shmid_ds tbuf_old;
  
  		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
  			return -EFAULT;

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

  /*

   * Calculate and add used RSS and swap pages of a shm.

   * Called with shm_ids.rwsem held as a reader

   */
  static void shm_add_rss_swap(struct shmid_kernel *shp,
  	unsigned long *rss_add, unsigned long *swp_add)
  {
  	struct inode *inode;

  	inode = file_inode(shp->shm_file);

  
  	if (is_file_hugepages(shp->shm_file)) {
  		struct address_space *mapping = inode->i_mapping;
  		struct hstate *h = hstate_file(shp->shm_file);
  		*rss_add += pages_per_huge_page(h) * mapping->nrpages;
  	} else {
  #ifdef CONFIG_SHMEM
  		struct shmem_inode_info *info = SHMEM_I(inode);

  		spin_lock_irq(&info->lock);

  		*rss_add += inode->i_mapping->nrpages;
  		*swp_add += info->swapped;

  		spin_unlock_irq(&info->lock);

  #else
  		*rss_add += inode->i_mapping->nrpages;
  #endif
  	}
  }
  
  /*

   * Called with shm_ids.rwsem 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 kern_ipc_perm *ipc;

  		struct shmid_kernel *shp;

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

  			continue;

  		shp = container_of(ipc, struct shmid_kernel, shm_perm);

  		shm_add_rss_swap(shp, rss, swp);

  
  		total++;

  	}
  }

  /*

   * This function handles some shmctl 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 shmctl_down(struct ipc_namespace *ns, int shmid, int cmd,

  		       struct shmid64_ds *shmid64)

  {

  	struct kern_ipc_perm *ipcp;

  	struct shmid_kernel *shp;

  	int err;

  	down_write(&shm_ids(ns).rwsem);

  	rcu_read_lock();

  	ipcp = ipcctl_obtain_check(ns, &shm_ids(ns), shmid, cmd,

  				      &shmid64->shm_perm, 0);

  	if (IS_ERR(ipcp)) {
  		err = PTR_ERR(ipcp);

  		goto out_unlock1;
  	}

  	shp = container_of(ipcp, struct shmid_kernel, shm_perm);

  	err = security_shm_shmctl(&shp->shm_perm, cmd);

  	if (err)

  		goto out_unlock1;

  	switch (cmd) {
  	case IPC_RMID:

  		ipc_lock_object(&shp->shm_perm);

  		/* do_shm_rmid unlocks the ipc object and rcu */

  		do_shm_rmid(ns, ipcp);
  		goto out_up;
  	case IPC_SET:

  		ipc_lock_object(&shp->shm_perm);

  		err = ipc_update_perm(&shmid64->shm_perm, ipcp);

  		if (err)

  			goto out_unlock0;

  		shp->shm_ctim = ktime_get_real_seconds();

  		break;
  	default:
  		err = -EINVAL;

  		goto out_unlock1;

  	}

  
  out_unlock0:
  	ipc_unlock_object(&shp->shm_perm);
  out_unlock1:
  	rcu_read_unlock();

  out_up:

  	up_write(&shm_ids(ns).rwsem);

  	return err;
  }

  static int shmctl_ipc_info(struct ipc_namespace *ns,
  			   struct shminfo64 *shminfo)

  {

  	int err = security_shm_shmctl(NULL, IPC_INFO);
  	if (!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;

  		down_read(&shm_ids(ns).rwsem);

  		err = ipc_get_maxidx(&shm_ids(ns));

  		up_read(&shm_ids(ns).rwsem);

  		if (err < 0)

  			err = 0;

  	}

  	return err;
  }

  static int shmctl_shm_info(struct ipc_namespace *ns,
  			   struct shm_info *shm_info)
  {
  	int err = security_shm_shmctl(NULL, SHM_INFO);
  	if (!err) {
  		memset(shm_info, 0, sizeof(*shm_info));

  		down_read(&shm_ids(ns).rwsem);

  		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_maxidx(&shm_ids(ns));

  		up_read(&shm_ids(ns).rwsem);

  		if (err < 0)
  			err = 0;

  	}

  	return err;
  }

  static int shmctl_stat(struct ipc_namespace *ns, int shmid,
  			int cmd, struct shmid64_ds *tbuf)
  {
  	struct shmid_kernel *shp;

  	int err;

  	memset(tbuf, 0, sizeof(*tbuf));

  	rcu_read_lock();

  	if (cmd == SHM_STAT || cmd == SHM_STAT_ANY) {

  		shp = shm_obtain_object(ns, shmid);
  		if (IS_ERR(shp)) {
  			err = PTR_ERR(shp);
  			goto out_unlock;
  		}

  	} else { /* IPC_STAT */

  		shp = shm_obtain_object_check(ns, shmid);
  		if (IS_ERR(shp)) {
  			err = PTR_ERR(shp);

  			goto out_unlock;

  		}

  	}

  	/*
  	 * Semantically SHM_STAT_ANY ought to be identical to
  	 * that functionality provided by the /proc/sysvipc/
  	 * interface. As such, only audit these calls and
  	 * do not do traditional S_IRUGO permission checks on
  	 * the ipc object.
  	 */
  	if (cmd == SHM_STAT_ANY)
  		audit_ipc_obj(&shp->shm_perm);
  	else {
  		err = -EACCES;
  		if (ipcperms(ns, &shp->shm_perm, S_IRUGO))
  			goto out_unlock;
  	}

  	err = security_shm_shmctl(&shp->shm_perm, cmd);

  	if (err)
  		goto out_unlock;

  	ipc_lock_object(&shp->shm_perm);
  
  	if (!ipc_valid_object(&shp->shm_perm)) {
  		ipc_unlock_object(&shp->shm_perm);
  		err = -EIDRM;
  		goto out_unlock;
  	}

  	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;

  #ifndef CONFIG_64BIT
  	tbuf->shm_atime_high = shp->shm_atim >> 32;
  	tbuf->shm_dtime_high = shp->shm_dtim >> 32;
  	tbuf->shm_ctime_high = shp->shm_ctim >> 32;
  #endif

  	tbuf->shm_cpid	= pid_vnr(shp->shm_cprid);
  	tbuf->shm_lpid	= pid_vnr(shp->shm_lprid);

  	tbuf->shm_nattch = shp->shm_nattch;

  	if (cmd == IPC_STAT) {
  		/*
  		 * As defined in SUS:
  		 * Return 0 on success
  		 */
  		err = 0;
  	} else {
  		/*
  		 * SHM_STAT and SHM_STAT_ANY (both Linux specific)
  		 * Return the full id, including the sequence number
  		 */
  		err = shp->shm_perm.id;
  	}

  	ipc_unlock_object(&shp->shm_perm);

  out_unlock:

  	rcu_read_unlock();

  	return err;
  }

  static int shmctl_do_lock(struct ipc_namespace *ns, int shmid, int cmd)

  {
  	struct shmid_kernel *shp;

  	struct file *shm_file;
  	int err;

  	rcu_read_lock();
  	shp = shm_obtain_object_check(ns, shmid);
  	if (IS_ERR(shp)) {
  		err = PTR_ERR(shp);
  		goto out_unlock1;

  	}

  	audit_ipc_obj(&(shp->shm_perm));

  	err = security_shm_shmctl(&shp->shm_perm, cmd);

  	if (err)
  		goto out_unlock1;

  	ipc_lock_object(&shp->shm_perm);

  	/* check if shm_destroy() is tearing down shp */
  	if (!ipc_valid_object(&shp->shm_perm)) {
  		err = -EIDRM;
  		goto out_unlock0;

  	}

  	if (!ns_capable(ns->user_ns, CAP_IPC_LOCK)) {
  		kuid_t euid = current_euid();

  		if (!uid_eq(euid, shp->shm_perm.uid) &&
  		    !uid_eq(euid, shp->shm_perm.cuid)) {
  			err = -EPERM;

  			goto out_unlock0;
  		}

  		if (cmd == SHM_LOCK && !rlimit(RLIMIT_MEMLOCK)) {
  			err = -EPERM;
  			goto out_unlock0;

  		}

  	}

  	shm_file = shp->shm_file;
  	if (is_file_hugepages(shm_file))
  		goto out_unlock0;

  	if (cmd == SHM_LOCK) {
  		struct user_struct *user = current_user();

  		err = shmem_lock(shm_file, 1, user);
  		if (!err && !(shp->shm_perm.mode & SHM_LOCKED)) {
  			shp->shm_perm.mode |= SHM_LOCKED;
  			shp->mlock_user = user;

  		}

  		goto out_unlock0;

  	}

  	/* SHM_UNLOCK */
  	if (!(shp->shm_perm.mode & SHM_LOCKED))
  		goto out_unlock0;
  	shmem_lock(shm_file, 0, shp->mlock_user);
  	shp->shm_perm.mode &= ~SHM_LOCKED;
  	shp->mlock_user = NULL;
  	get_file(shm_file);
  	ipc_unlock_object(&shp->shm_perm);
  	rcu_read_unlock();
  	shmem_unlock_mapping(shm_file->f_mapping);
  
  	fput(shm_file);
  	return err;

  out_unlock0:
  	ipc_unlock_object(&shp->shm_perm);
  out_unlock1:

  	rcu_read_unlock();

  	return err;
  }

  long ksys_shmctl(int shmid, int cmd, struct shmid_ds __user *buf)

  {

  	int err, version;
  	struct ipc_namespace *ns;

  	struct shmid64_ds sem64;

  	if (cmd < 0 || shmid < 0)
  		return -EINVAL;

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

  	case IPC_INFO: {
  		struct shminfo64 shminfo;
  		err = shmctl_ipc_info(ns, &shminfo);
  		if (err < 0)
  			return err;
  		if (copy_shminfo_to_user(buf, &shminfo, version))
  			err = -EFAULT;
  		return err;
  	}
  	case SHM_INFO: {
  		struct shm_info shm_info;
  		err = shmctl_shm_info(ns, &shm_info);
  		if (err < 0)
  			return err;
  		if (copy_to_user(buf, &shm_info, sizeof(shm_info)))
  			err = -EFAULT;
  		return err;
  	}

  	case SHM_STAT:

  	case SHM_STAT_ANY:

  	case IPC_STAT: {

  		err = shmctl_stat(ns, shmid, cmd, &sem64);

  		if (err < 0)
  			return err;

  		if (copy_shmid_to_user(buf, &sem64, version))

  			err = -EFAULT;
  		return err;
  	}

  	case IPC_SET:

  		if (copy_shmid_from_user(&sem64, buf, version))

  			return -EFAULT;

  		/* fallthru */

  	case IPC_RMID:

  		return shmctl_down(ns, shmid, cmd, &sem64);

  	case SHM_LOCK:
  	case SHM_UNLOCK:

  		return shmctl_do_lock(ns, shmid, cmd);
  	default:
  		return -EINVAL;
  	}
  }

  SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, struct shmid_ds __user *, buf)
  {
  	return ksys_shmctl(shmid, cmd, buf);
  }

  #ifdef CONFIG_COMPAT
  
  struct compat_shmid_ds {
  	struct compat_ipc_perm shm_perm;
  	int shm_segsz;
  	compat_time_t shm_atime;
  	compat_time_t shm_dtime;
  	compat_time_t shm_ctime;
  	compat_ipc_pid_t shm_cpid;
  	compat_ipc_pid_t shm_lpid;
  	unsigned short shm_nattch;
  	unsigned short shm_unused;
  	compat_uptr_t shm_unused2;
  	compat_uptr_t shm_unused3;
  };

  struct compat_shminfo64 {
  	compat_ulong_t shmmax;
  	compat_ulong_t shmmin;
  	compat_ulong_t shmmni;
  	compat_ulong_t shmseg;
  	compat_ulong_t shmall;
  	compat_ulong_t __unused1;
  	compat_ulong_t __unused2;
  	compat_ulong_t __unused3;
  	compat_ulong_t __unused4;
  };

  struct compat_shm_info {
  	compat_int_t used_ids;
  	compat_ulong_t shm_tot, shm_rss, shm_swp;
  	compat_ulong_t swap_attempts, swap_successes;
  };

  static int copy_compat_shminfo_to_user(void __user *buf, struct shminfo64 *in,
  					int version)
  {
  	if (in->shmmax > INT_MAX)
  		in->shmmax = INT_MAX;
  	if (version == IPC_64) {
  		struct compat_shminfo64 info;
  		memset(&info, 0, sizeof(info));
  		info.shmmax = in->shmmax;
  		info.shmmin = in->shmmin;
  		info.shmmni = in->shmmni;
  		info.shmseg = in->shmseg;
  		info.shmall = in->shmall;
  		return copy_to_user(buf, &info, sizeof(info));
  	} else {
  		struct shminfo info;
  		memset(&info, 0, sizeof(info));
  		info.shmmax = in->shmmax;
  		info.shmmin = in->shmmin;
  		info.shmmni = in->shmmni;
  		info.shmseg = in->shmseg;
  		info.shmall = in->shmall;
  		return copy_to_user(buf, &info, sizeof(info));
  	}
  }

  static int put_compat_shm_info(struct shm_info *ip,
  				struct compat_shm_info __user *uip)
  {
  	struct compat_shm_info info;
  
  	memset(&info, 0, sizeof(info));
  	info.used_ids = ip->used_ids;
  	info.shm_tot = ip->shm_tot;
  	info.shm_rss = ip->shm_rss;
  	info.shm_swp = ip->shm_swp;
  	info.swap_attempts = ip->swap_attempts;
  	info.swap_successes = ip->swap_successes;

  	return copy_to_user(uip, &info, sizeof(info));

  }

  static int copy_compat_shmid_to_user(void __user *buf, struct shmid64_ds *in,
  					int version)
  {
  	if (version == IPC_64) {
  		struct compat_shmid64_ds v;
  		memset(&v, 0, sizeof(v));

  		to_compat_ipc64_perm(&v.shm_perm, &in->shm_perm);

  		v.shm_atime	 = lower_32_bits(in->shm_atime);
  		v.shm_atime_high = upper_32_bits(in->shm_atime);
  		v.shm_dtime	 = lower_32_bits(in->shm_dtime);
  		v.shm_dtime_high = upper_32_bits(in->shm_dtime);
  		v.shm_ctime	 = lower_32_bits(in->shm_ctime);
  		v.shm_ctime_high = upper_32_bits(in->shm_ctime);

  		v.shm_segsz = in->shm_segsz;
  		v.shm_nattch = in->shm_nattch;
  		v.shm_cpid = in->shm_cpid;
  		v.shm_lpid = in->shm_lpid;
  		return copy_to_user(buf, &v, sizeof(v));
  	} else {
  		struct compat_shmid_ds v;
  		memset(&v, 0, sizeof(v));

  		to_compat_ipc_perm(&v.shm_perm, &in->shm_perm);

  		v.shm_perm.key = in->shm_perm.key;

  		v.shm_atime = in->shm_atime;
  		v.shm_dtime = in->shm_dtime;
  		v.shm_ctime = in->shm_ctime;
  		v.shm_segsz = in->shm_segsz;
  		v.shm_nattch = in->shm_nattch;
  		v.shm_cpid = in->shm_cpid;
  		v.shm_lpid = in->shm_lpid;
  		return copy_to_user(buf, &v, sizeof(v));
  	}
  }

  static int copy_compat_shmid_from_user(struct shmid64_ds *out, void __user *buf,
  					int version)
  {
  	memset(out, 0, sizeof(*out));
  	if (version == IPC_64) {

  		struct compat_shmid64_ds __user *p = buf;

  		return get_compat_ipc64_perm(&out->shm_perm, &p->shm_perm);

  	} else {

  		struct compat_shmid_ds __user *p = buf;

  		return get_compat_ipc_perm(&out->shm_perm, &p->shm_perm);

  	}

  }

  long compat_ksys_shmctl(int shmid, int cmd, void __user *uptr)

  {
  	struct ipc_namespace *ns;
  	struct shmid64_ds sem64;
  	int version = compat_ipc_parse_version(&cmd);
  	int err;

  	ns = current->nsproxy->ipc_ns;
  
  	if (cmd < 0 || shmid < 0)
  		return -EINVAL;

  	switch (cmd) {
  	case IPC_INFO: {
  		struct shminfo64 shminfo;
  		err = shmctl_ipc_info(ns, &shminfo);
  		if (err < 0)
  			return err;
  		if (copy_compat_shminfo_to_user(uptr, &shminfo, version))
  			err = -EFAULT;
  		return err;
  	}
  	case SHM_INFO: {
  		struct shm_info shm_info;
  		err = shmctl_shm_info(ns, &shm_info);
  		if (err < 0)
  			return err;
  		if (put_compat_shm_info(&shm_info, uptr))
  			err = -EFAULT;

  		return err;

  	}

  	case IPC_STAT:

  	case SHM_STAT_ANY:

  	case SHM_STAT:
  		err = shmctl_stat(ns, shmid, cmd, &sem64);
  		if (err < 0)
  			return err;

  		if (copy_compat_shmid_to_user(uptr, &sem64, version))

  			err = -EFAULT;
  		return err;
  
  	case IPC_SET:
  		if (copy_compat_shmid_from_user(&sem64, uptr, version))
  			return -EFAULT;
  		/* fallthru */
  	case IPC_RMID:
  		return shmctl_down(ns, shmid, cmd, &sem64);
  	case SHM_LOCK:
  	case SHM_UNLOCK:
  		return shmctl_do_lock(ns, shmid, cmd);
  		break;

  	default:

  		return -EINVAL;

  	}

  	return err;
  }

  
  COMPAT_SYSCALL_DEFINE3(shmctl, int, shmid, int, cmd, void __user *, uptr)
  {
  	return compat_ksys_shmctl(shmid, cmd, uptr);
  }

  #endif

  
  /*
   * 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, unsigned long shmlba)

  {
  	struct shmid_kernel *shp;

  	unsigned long addr = (unsigned long)shmaddr;

  	unsigned long size;

  	struct file *file, *base;

  	int    err;

  	unsigned long flags = MAP_SHARED;

  	unsigned long prot;

  	int acc_mode;

  	struct ipc_namespace *ns;

  	struct shm_file_data *sfd;

  	int f_flags;

  	unsigned long populate = 0;

  	err = -EINVAL;
  	if (shmid < 0)

  		goto out;

  
  	if (addr) {

  		if (addr & (shmlba - 1)) {

  			if (shmflg & SHM_RND) {

  				addr &= ~(shmlba - 1);  /* round down */

  
  				/*
  				 * Ensure that the round-down is non-nil
  				 * when remapping. This can happen for
  				 * cases when addr < shmlba.
  				 */
  				if (!addr && (shmflg & SHM_REMAP))
  					goto out;
  			} else

  #ifndef __ARCH_FORCE_SHMLBA
  				if (addr & ~PAGE_MASK)
  #endif

  					goto out;

  		}

  		flags |= MAP_FIXED;
  	} else if ((shmflg & SHM_REMAP))
  		goto out;

  
  	if (shmflg & SHM_RDONLY) {
  		prot = PROT_READ;

  		acc_mode = S_IRUGO;

  		f_flags = O_RDONLY;

  	} else {
  		prot = PROT_READ | PROT_WRITE;

  		acc_mode = S_IRUGO | S_IWUGO;

  		f_flags = O_RDWR;

  	}
  	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;

  	rcu_read_lock();
  	shp = shm_obtain_object_check(ns, shmid);

  	if (IS_ERR(shp)) {
  		err = PTR_ERR(shp);

  		goto out_unlock;

  	}

  
  	err = -EACCES;

  	if (ipcperms(ns, &shp->shm_perm, acc_mode))

  		goto out_unlock;

  	err = security_shm_shmat(&shp->shm_perm, shmaddr, shmflg);

  	if (err)
  		goto out_unlock;

  	ipc_lock_object(&shp->shm_perm);

  
  	/* check if shm_destroy() is tearing down shp */

  	if (!ipc_valid_object(&shp->shm_perm)) {