/*
    File: fs/xattr.c
  
    Extended attribute handling.
  
    Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
    Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
    Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
   */
  #include <linux/fs.h>
  #include <linux/slab.h>

  #include <linux/file.h>
  #include <linux/xattr.h>

  #include <linux/mount.h>

  #include <linux/namei.h>
  #include <linux/security.h>

  #include <linux/evm.h>

  #include <linux/syscalls.h>

  #include <linux/export.h>

  #include <linux/fsnotify.h>

  #include <linux/audit.h>

  #include <linux/vmalloc.h>

  #include <linux/posix_acl_xattr.h>

  #include <asm/uaccess.h>

  /*
   * Check permissions for extended attribute access.  This is a bit complicated
   * because different namespaces have very different rules.
   */
  static int
  xattr_permission(struct inode *inode, const char *name, int mask)
  {
  	/*
  	 * We can never set or remove an extended attribute on a read-only
  	 * filesystem  or on an immutable / append-only inode.
  	 */
  	if (mask & MAY_WRITE) {

  		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  			return -EPERM;
  	}
  
  	/*
  	 * No restriction for security.* and system.* from the VFS.  Decision
  	 * on these is left to the underlying filesystem / security module.
  	 */
  	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
  	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  		return 0;
  
  	/*

  	 * The trusted.* namespace can only be accessed by privileged users.

  	 */

  	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
  		if (!capable(CAP_SYS_ADMIN))
  			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  		return 0;
  	}

  	/*
  	 * In the user.* namespace, only regular files and directories can have

  	 * extended attributes. For sticky directories, only the owner and

  	 * privileged users can write attributes.

  	 */

  	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {

  		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))

  			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;

  		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&

  		    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))

  			return -EPERM;
  	}

  	return inode_permission(inode, mask);

  }

  /**
   *  __vfs_setxattr_noperm - perform setxattr operation without performing
   *  permission checks.
   *
   *  @dentry - object to perform setxattr on
   *  @name - xattr name to set
   *  @value - value to set @name to
   *  @size - size of @value
   *  @flags - flags to pass into filesystem operations
   *
   *  returns the result of the internal setxattr or setsecurity operations.
   *
   *  This function requires the caller to lock the inode's i_mutex before it
   *  is executed. It also assumes that the caller will make the appropriate
   *  permission checks.
   */
  int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
  		const void *value, size_t size, int flags)

  {
  	struct inode *inode = dentry->d_inode;

  	int error = -EOPNOTSUPP;

  	int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
  				   XATTR_SECURITY_PREFIX_LEN);

  	if (issec)
  		inode->i_flags &= ~S_NOSEC;

  	if (inode->i_op->setxattr) {
  		error = inode->i_op->setxattr(dentry, name, value, size, flags);
  		if (!error) {
  			fsnotify_xattr(dentry);
  			security_inode_post_setxattr(dentry, name, value,
  						     size, flags);
  		}

  	} else if (issec) {

  		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;

  		error = security_inode_setsecurity(inode, suffix, value,
  						   size, flags);
  		if (!error)
  			fsnotify_xattr(dentry);
  	}

  
  	return error;
  }
  
  
  int
  vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
  		size_t size, int flags)
  {
  	struct inode *inode = dentry->d_inode;
  	int error;
  
  	error = xattr_permission(inode, name, MAY_WRITE);
  	if (error)
  		return error;
  
  	mutex_lock(&inode->i_mutex);
  	error = security_inode_setxattr(dentry, name, value, size, flags);
  	if (error)
  		goto out;
  
  	error = __vfs_setxattr_noperm(dentry, name, value, size, flags);

  out:
  	mutex_unlock(&inode->i_mutex);
  	return error;
  }
  EXPORT_SYMBOL_GPL(vfs_setxattr);
  
  ssize_t

  xattr_getsecurity(struct inode *inode, const char *name, void *value,
  			size_t size)
  {
  	void *buffer = NULL;
  	ssize_t len;
  
  	if (!value || !size) {
  		len = security_inode_getsecurity(inode, name, &buffer, false);
  		goto out_noalloc;
  	}
  
  	len = security_inode_getsecurity(inode, name, &buffer, true);
  	if (len < 0)
  		return len;
  	if (size < len) {
  		len = -ERANGE;
  		goto out;
  	}
  	memcpy(value, buffer, len);
  out:
  	security_release_secctx(buffer, len);
  out_noalloc:
  	return len;
  }
  EXPORT_SYMBOL_GPL(xattr_getsecurity);

  /*
   * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
   *
   * Allocate memory, if not already allocated, or re-allocate correct size,
   * before retrieving the extended attribute.
   *
   * Returns the result of alloc, if failed, or the getxattr operation.
   */
  ssize_t
  vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
  		   size_t xattr_size, gfp_t flags)
  {
  	struct inode *inode = dentry->d_inode;
  	char *value = *xattr_value;
  	int error;
  
  	error = xattr_permission(inode, name, MAY_READ);
  	if (error)
  		return error;
  
  	if (!inode->i_op->getxattr)
  		return -EOPNOTSUPP;
  
  	error = inode->i_op->getxattr(dentry, name, NULL, 0);
  	if (error < 0)
  		return error;
  
  	if (!value || (error > xattr_size)) {
  		value = krealloc(*xattr_value, error + 1, flags);
  		if (!value)
  			return -ENOMEM;
  		memset(value, 0, error + 1);
  	}
  
  	error = inode->i_op->getxattr(dentry, name, value, error);
  	*xattr_value = value;
  	return error;
  }
  
  /* Compare an extended attribute value with the given value */
  int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
  		  const char *value, size_t size, gfp_t flags)
  {
  	char *xattr_value = NULL;
  	int rc;
  
  	rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
  	if (rc < 0)
  		return rc;
  
  	if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
  		rc = -EINVAL;
  	else
  		rc = 0;
  	kfree(xattr_value);
  	return rc;
  }

  ssize_t

  vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)

  {
  	struct inode *inode = dentry->d_inode;
  	int error;

  	error = xattr_permission(inode, name, MAY_READ);
  	if (error)
  		return error;

  	error = security_inode_getxattr(dentry, name);
  	if (error)
  		return error;

  	if (!strncmp(name, XATTR_SECURITY_PREFIX,

  				XATTR_SECURITY_PREFIX_LEN)) {
  		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;

  		int ret = xattr_getsecurity(inode, suffix, value, size);

  		/*
  		 * Only overwrite the return value if a security module
  		 * is actually active.
  		 */

  		if (ret == -EOPNOTSUPP)
  			goto nolsm;
  		return ret;

  	}

  nolsm:
  	if (inode->i_op->getxattr)
  		error = inode->i_op->getxattr(dentry, name, value, size);
  	else
  		error = -EOPNOTSUPP;

  
  	return error;
  }
  EXPORT_SYMBOL_GPL(vfs_getxattr);

  ssize_t
  vfs_listxattr(struct dentry *d, char *list, size_t size)
  {
  	ssize_t error;
  
  	error = security_inode_listxattr(d);
  	if (error)
  		return error;
  	error = -EOPNOTSUPP;

  	if (d->d_inode->i_op->listxattr) {

  		error = d->d_inode->i_op->listxattr(d, list, size);
  	} else {
  		error = security_inode_listsecurity(d->d_inode, list, size);
  		if (size && error > size)
  			error = -ERANGE;
  	}
  	return error;
  }
  EXPORT_SYMBOL_GPL(vfs_listxattr);

  int

  vfs_removexattr(struct dentry *dentry, const char *name)

  {
  	struct inode *inode = dentry->d_inode;
  	int error;
  
  	if (!inode->i_op->removexattr)
  		return -EOPNOTSUPP;

  	error = xattr_permission(inode, name, MAY_WRITE);
  	if (error)
  		return error;

  	mutex_lock(&inode->i_mutex);

  	error = security_inode_removexattr(dentry, name);

  	if (error) {
  		mutex_unlock(&inode->i_mutex);

  		return error;

  	}

  	error = inode->i_op->removexattr(dentry, name);
  	mutex_unlock(&inode->i_mutex);

  	if (!error) {

  		fsnotify_xattr(dentry);

  		evm_inode_post_removexattr(dentry, name);
  	}

  	return error;
  }
  EXPORT_SYMBOL_GPL(vfs_removexattr);

  /*
   * Extended attribute SET operations
   */
  static long

  setxattr(struct dentry *d, const char __user *name, const void __user *value,

  	 size_t size, int flags)
  {
  	int error;
  	void *kvalue = NULL;

  	void *vvalue = NULL;	/* If non-NULL, we used vmalloc() */

  	char kname[XATTR_NAME_MAX + 1];
  
  	if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
  		return -EINVAL;
  
  	error = strncpy_from_user(kname, name, sizeof(kname));
  	if (error == 0 || error == sizeof(kname))
  		error = -ERANGE;
  	if (error < 0)
  		return error;
  
  	if (size) {
  		if (size > XATTR_SIZE_MAX)
  			return -E2BIG;

  		kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
  		if (!kvalue) {
  			vvalue = vmalloc(size);
  			if (!vvalue)
  				return -ENOMEM;
  			kvalue = vvalue;
  		}
  		if (copy_from_user(kvalue, value, size)) {
  			error = -EFAULT;
  			goto out;
  		}

  		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
  		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
  			posix_acl_fix_xattr_from_user(kvalue, size);

  	}

  	error = vfs_setxattr(d, kname, kvalue, size, flags);

  out:
  	if (vvalue)
  		vfree(vvalue);
  	else
  		kfree(kvalue);

  	return error;
  }

  SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
  		const char __user *, name, const void __user *, value,
  		size_t, size, int, flags)

  {

  	struct path path;

  	int error;

  	unsigned int lookup_flags = LOOKUP_FOLLOW;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = mnt_want_write(path.mnt);

  	if (!error) {

  		error = setxattr(path.dentry, name, value, size, flags);
  		mnt_drop_write(path.mnt);

  	}

  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
  		const char __user *, name, const void __user *, value,
  		size_t, size, int, flags)

  {

  	struct path path;

  	int error;

  	unsigned int lookup_flags = 0;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = mnt_want_write(path.mnt);

  	if (!error) {

  		error = setxattr(path.dentry, name, value, size, flags);
  		mnt_drop_write(path.mnt);

  	}

  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
  		const void __user *,value, size_t, size, int, flags)

  {

  	struct fd f = fdget(fd);

  	struct dentry *dentry;

  	int error = -EBADF;

  	if (!f.file)

  		return error;

  	dentry = f.file->f_path.dentry;

  	audit_inode(NULL, dentry, 0);

  	error = mnt_want_write_file(f.file);

  	if (!error) {
  		error = setxattr(dentry, name, value, size, flags);

  		mnt_drop_write_file(f.file);

  	}

  	fdput(f);

  	return error;
  }
  
  /*
   * Extended attribute GET operations
   */
  static ssize_t

  getxattr(struct dentry *d, const char __user *name, void __user *value,
  	 size_t size)

  {
  	ssize_t error;
  	void *kvalue = NULL;

  	void *vvalue = NULL;

  	char kname[XATTR_NAME_MAX + 1];
  
  	error = strncpy_from_user(kname, name, sizeof(kname));
  	if (error == 0 || error == sizeof(kname))
  		error = -ERANGE;
  	if (error < 0)
  		return error;
  
  	if (size) {
  		if (size > XATTR_SIZE_MAX)
  			size = XATTR_SIZE_MAX;

  		kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
  		if (!kvalue) {
  			vvalue = vmalloc(size);
  			if (!vvalue)
  				return -ENOMEM;
  			kvalue = vvalue;
  		}

  	}

  	error = vfs_getxattr(d, kname, kvalue, size);

  	if (error > 0) {

  		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
  		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
  			posix_acl_fix_xattr_to_user(kvalue, size);

  		if (size && copy_to_user(value, kvalue, error))
  			error = -EFAULT;
  	} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
  		/* The file system tried to returned a value bigger
  		   than XATTR_SIZE_MAX bytes. Not possible. */
  		error = -E2BIG;

  	}

  	if (vvalue)
  		vfree(vvalue);
  	else
  		kfree(kvalue);

  	return error;
  }

  SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
  		const char __user *, name, void __user *, value, size_t, size)

  {

  	struct path path;

  	ssize_t error;

  	unsigned int lookup_flags = LOOKUP_FOLLOW;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = getxattr(path.dentry, name, value, size);
  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
  		const char __user *, name, void __user *, value, size_t, size)

  {

  	struct path path;

  	ssize_t error;

  	unsigned int lookup_flags = 0;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = getxattr(path.dentry, name, value, size);
  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
  		void __user *, value, size_t, size)

  {

  	struct fd f = fdget(fd);

  	ssize_t error = -EBADF;

  	if (!f.file)

  		return error;

  	audit_inode(NULL, f.file->f_path.dentry, 0);

  	error = getxattr(f.file->f_path.dentry, name, value, size);
  	fdput(f);

  	return error;
  }
  
  /*
   * Extended attribute LIST operations
   */
  static ssize_t
  listxattr(struct dentry *d, char __user *list, size_t size)
  {
  	ssize_t error;
  	char *klist = NULL;

  	char *vlist = NULL;	/* If non-NULL, we used vmalloc() */

  
  	if (size) {
  		if (size > XATTR_LIST_MAX)
  			size = XATTR_LIST_MAX;

  		klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);

  		if (!klist) {
  			vlist = vmalloc(size);
  			if (!vlist)
  				return -ENOMEM;
  			klist = vlist;
  		}

  	}

  	error = vfs_listxattr(d, klist, size);

  	if (error > 0) {
  		if (size && copy_to_user(list, klist, error))
  			error = -EFAULT;
  	} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
  		/* The file system tried to returned a list bigger
  		   than XATTR_LIST_MAX bytes. Not possible. */
  		error = -E2BIG;

  	}

  	if (vlist)
  		vfree(vlist);
  	else
  		kfree(klist);

  	return error;
  }

  SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
  		size_t, size)

  {

  	struct path path;

  	ssize_t error;

  	unsigned int lookup_flags = LOOKUP_FOLLOW;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = listxattr(path.dentry, list, size);
  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
  		size_t, size)

  {

  	struct path path;

  	ssize_t error;

  	unsigned int lookup_flags = 0;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = listxattr(path.dentry, list, size);
  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)

  {

  	struct fd f = fdget(fd);

  	ssize_t error = -EBADF;

  	if (!f.file)

  		return error;

  	audit_inode(NULL, f.file->f_path.dentry, 0);

  	error = listxattr(f.file->f_path.dentry, list, size);
  	fdput(f);

  	return error;
  }
  
  /*
   * Extended attribute REMOVE operations
   */
  static long

  removexattr(struct dentry *d, const char __user *name)

  {
  	int error;
  	char kname[XATTR_NAME_MAX + 1];
  
  	error = strncpy_from_user(kname, name, sizeof(kname));
  	if (error == 0 || error == sizeof(kname))
  		error = -ERANGE;
  	if (error < 0)
  		return error;

  	return vfs_removexattr(d, kname);

  }

  SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
  		const char __user *, name)

  {

  	struct path path;

  	int error;

  	unsigned int lookup_flags = LOOKUP_FOLLOW;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = mnt_want_write(path.mnt);

  	if (!error) {

  		error = removexattr(path.dentry, name);
  		mnt_drop_write(path.mnt);

  	}

  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
  		const char __user *, name)

  {

  	struct path path;

  	int error;

  	unsigned int lookup_flags = 0;
  retry:
  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

  	if (error)
  		return error;

  	error = mnt_want_write(path.mnt);

  	if (!error) {

  		error = removexattr(path.dentry, name);
  		mnt_drop_write(path.mnt);

  	}

  	path_put(&path);

  	if (retry_estale(error, lookup_flags)) {
  		lookup_flags |= LOOKUP_REVAL;
  		goto retry;
  	}

  	return error;
  }

  SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)

  {

  	struct fd f = fdget(fd);

  	struct dentry *dentry;

  	int error = -EBADF;

  	if (!f.file)

  		return error;

  	dentry = f.file->f_path.dentry;

  	audit_inode(NULL, dentry, 0);

  	error = mnt_want_write_file(f.file);

  	if (!error) {
  		error = removexattr(dentry, name);

  		mnt_drop_write_file(f.file);

  	}

  	fdput(f);

  	return error;
  }
  
  
  static const char *
  strcmp_prefix(const char *a, const char *a_prefix)
  {
  	while (*a_prefix && *a == *a_prefix) {
  		a++;
  		a_prefix++;
  	}
  	return *a_prefix ? NULL : a;
  }
  
  /*
   * In order to implement different sets of xattr operations for each xattr
   * prefix with the generic xattr API, a filesystem should create a
   * null-terminated array of struct xattr_handler (one for each prefix) and
   * hang a pointer to it off of the s_xattr field of the superblock.
   *
   * The generic_fooxattr() functions will use this list to dispatch xattr
   * operations to the correct xattr_handler.
   */
  #define for_each_xattr_handler(handlers, handler)		\
  		for ((handler) = *(handlers)++;			\
  			(handler) != NULL;			\
  			(handler) = *(handlers)++)
  
  /*
   * Find the xattr_handler with the matching prefix.
   */

  static const struct xattr_handler *
  xattr_resolve_name(const struct xattr_handler **handlers, const char **name)

  {

  	const struct xattr_handler *handler;

  
  	if (!*name)
  		return NULL;
  
  	for_each_xattr_handler(handlers, handler) {
  		const char *n = strcmp_prefix(*name, handler->prefix);
  		if (n) {
  			*name = n;
  			break;
  		}
  	}
  	return handler;
  }
  
  /*
   * Find the handler for the prefix and dispatch its get() operation.
   */
  ssize_t
  generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
  {

  	const struct xattr_handler *handler;

  	handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);

  	if (!handler)
  		return -EOPNOTSUPP;

  	return handler->get(dentry, name, buffer, size, handler->flags);

  }
  
  /*
   * Combine the results of the list() operation from every xattr_handler in the
   * list.
   */
  ssize_t
  generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
  {

  	const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;

  	unsigned int size = 0;
  
  	if (!buffer) {

  		for_each_xattr_handler(handlers, handler) {
  			size += handler->list(dentry, NULL, 0, NULL, 0,
  					      handler->flags);
  		}

  	} else {
  		char *buf = buffer;
  
  		for_each_xattr_handler(handlers, handler) {

  			size = handler->list(dentry, buf, buffer_size,
  					     NULL, 0, handler->flags);

  			if (size > buffer_size)
  				return -ERANGE;
  			buf += size;
  			buffer_size -= size;
  		}
  		size = buf - buffer;
  	}
  	return size;
  }
  
  /*
   * Find the handler for the prefix and dispatch its set() operation.
   */
  int
  generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
  {

  	const struct xattr_handler *handler;

  
  	if (size == 0)
  		value = "";  /* empty EA, do not remove */

  	handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);

  	if (!handler)
  		return -EOPNOTSUPP;

  	return handler->set(dentry, name, value, size, flags, handler->flags);

  }
  
  /*
   * Find the handler for the prefix and dispatch its set() operation to remove
   * any associated extended attribute.
   */
  int
  generic_removexattr(struct dentry *dentry, const char *name)
  {

  	const struct xattr_handler *handler;

  	handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);

  	if (!handler)
  		return -EOPNOTSUPP;

  	return handler->set(dentry, name, NULL, 0,
  			    XATTR_REPLACE, handler->flags);

  }
  
  EXPORT_SYMBOL(generic_getxattr);
  EXPORT_SYMBOL(generic_listxattr);
  EXPORT_SYMBOL(generic_setxattr);
  EXPORT_SYMBOL(generic_removexattr);

  
  /*
   * Allocate new xattr and copy in the value; but leave the name to callers.
   */
  struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
  {
  	struct simple_xattr *new_xattr;
  	size_t len;
  
  	/* wrap around? */
  	len = sizeof(*new_xattr) + size;
  	if (len <= sizeof(*new_xattr))
  		return NULL;
  
  	new_xattr = kmalloc(len, GFP_KERNEL);
  	if (!new_xattr)
  		return NULL;
  
  	new_xattr->size = size;
  	memcpy(new_xattr->value, value, size);
  	return new_xattr;
  }
  
  /*
   * xattr GET operation for in-memory/pseudo filesystems
   */
  int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
  		     void *buffer, size_t size)
  {
  	struct simple_xattr *xattr;
  	int ret = -ENODATA;
  
  	spin_lock(&xattrs->lock);
  	list_for_each_entry(xattr, &xattrs->head, list) {
  		if (strcmp(name, xattr->name))
  			continue;
  
  		ret = xattr->size;
  		if (buffer) {
  			if (size < xattr->size)
  				ret = -ERANGE;
  			else
  				memcpy(buffer, xattr->value, xattr->size);
  		}
  		break;
  	}
  	spin_unlock(&xattrs->lock);
  	return ret;
  }
  
  static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
  			      const void *value, size_t size, int flags)
  {
  	struct simple_xattr *xattr;

  	struct simple_xattr *new_xattr = NULL;

  	int err = 0;
  
  	/* value == NULL means remove */
  	if (value) {
  		new_xattr = simple_xattr_alloc(value, size);
  		if (!new_xattr)
  			return -ENOMEM;
  
  		new_xattr->name = kstrdup(name, GFP_KERNEL);
  		if (!new_xattr->name) {
  			kfree(new_xattr);
  			return -ENOMEM;
  		}
  	}
  
  	spin_lock(&xattrs->lock);
  	list_for_each_entry(xattr, &xattrs->head, list) {
  		if (!strcmp(name, xattr->name)) {
  			if (flags & XATTR_CREATE) {
  				xattr = new_xattr;
  				err = -EEXIST;
  			} else if (new_xattr) {
  				list_replace(&xattr->list, &new_xattr->list);
  			} else {
  				list_del(&xattr->list);
  			}
  			goto out;
  		}
  	}
  	if (flags & XATTR_REPLACE) {
  		xattr = new_xattr;
  		err = -ENODATA;
  	} else {
  		list_add(&new_xattr->list, &xattrs->head);
  		xattr = NULL;
  	}
  out:
  	spin_unlock(&xattrs->lock);
  	if (xattr) {
  		kfree(xattr->name);
  		kfree(xattr);
  	}
  	return err;
  
  }

  /**
   * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
   * @xattrs: target simple_xattr list
   * @name: name of the new extended attribute
   * @value: value of the new xattr. If %NULL, will remove the attribute
   * @size: size of the new xattr
   * @flags: %XATTR_{CREATE|REPLACE}
   *
   * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
   * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
   * otherwise, fails with -ENODATA.
   *
   * Returns 0 on success, -errno on failure.

   */
  int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
  		     const void *value, size_t size, int flags)
  {
  	if (size == 0)
  		value = ""; /* empty EA, do not remove */
  	return __simple_xattr_set(xattrs, name, value, size, flags);
  }
  
  /*
   * xattr REMOVE operation for in-memory/pseudo filesystems
   */
  int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
  {
  	return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
  }
  
  static bool xattr_is_trusted(const char *name)
  {
  	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
  }
  
  /*
   * xattr LIST operation for in-memory/pseudo filesystems
   */
  ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
  			  size_t size)
  {
  	bool trusted = capable(CAP_SYS_ADMIN);
  	struct simple_xattr *xattr;
  	size_t used = 0;
  
  	spin_lock(&xattrs->lock);
  	list_for_each_entry(xattr, &xattrs->head, list) {
  		size_t len;
  
  		/* skip "trusted." attributes for unprivileged callers */
  		if (!trusted && xattr_is_trusted(xattr->name))
  			continue;
  
  		len = strlen(xattr->name) + 1;
  		used += len;
  		if (buffer) {
  			if (size < used) {
  				used = -ERANGE;
  				break;
  			}
  			memcpy(buffer, xattr->name, len);
  			buffer += len;
  		}
  	}
  	spin_unlock(&xattrs->lock);
  
  	return used;
  }

  /*
   * Adds an extended attribute to the list
   */

  void simple_xattr_list_add(struct simple_xattrs *xattrs,
  			   struct simple_xattr *new_xattr)
  {
  	spin_lock(&xattrs->lock);
  	list_add(&new_xattr->list, &xattrs->head);
  	spin_unlock(&xattrs->lock);
  }