[mirror_ubuntu-artful-kernel.git] / fs / fhandle.c

#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/exportfs.h>
#include <linux/fs_struct.h>
#include <linux/fsnotify.h>
#include <asm/uaccess.h>
#include "internal.h"

static long do_sys_name_to_handle(struct path *path,
				  struct file_handle __user *ufh,
				  int __user *mnt_id)
{
	long retval;
	struct file_handle f_handle;
	int handle_dwords, handle_bytes;
	struct file_handle *handle = NULL;

	/*
	 * We need t make sure wether the file system
	 * support decoding of the file handle
	 */
	if (!path->mnt->mnt_sb->s_export_op ||
	    !path->mnt->mnt_sb->s_export_op->fh_to_dentry)
		return -EOPNOTSUPP;

	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
		return -EFAULT;

	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
		return -EINVAL;

	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
			 GFP_KERNEL);
	if (!handle)
		return -ENOMEM;

	/* convert handle size to  multiple of sizeof(u32) */
	handle_dwords = f_handle.handle_bytes >> 2;

	/* we ask for a non connected handle */
	retval = exportfs_encode_fh(path->dentry,
				    (struct fid *)handle->f_handle,
				    &handle_dwords,  0);
	handle->handle_type = retval;
	/* convert handle size to bytes */
	handle_bytes = handle_dwords * sizeof(u32);
	handle->handle_bytes = handle_bytes;
	if ((handle->handle_bytes > f_handle.handle_bytes) ||
	    (retval == 255) || (retval == -ENOSPC)) {
		/* As per old exportfs_encode_fh documentation
		 * we could return ENOSPC to indicate overflow
		 * But file system returned 255 always. So handle
		 * both the values
		 */
		/*
		 * set the handle size to zero so we copy only
		 * non variable part of the file_handle
		 */
		handle_bytes = 0;
		retval = -EOVERFLOW;
	} else
		retval = 0;
	/* copy the mount id */
	if (copy_to_user(mnt_id, &path->mnt->mnt_id, sizeof(*mnt_id)) ||
	    copy_to_user(ufh, handle,
			 sizeof(struct file_handle) + handle_bytes))
		retval = -EFAULT;
	kfree(handle);
	return retval;
}

/**
 * sys_name_to_handle_at: convert name to handle
 * @dfd: directory relative to which name is interpreted if not absolute
 * @name: name that should be converted to handle.
 * @handle: resulting file handle
 * @mnt_id: mount id of the file system containing the file
 * @flag: flag value to indicate whether to follow symlink or not
 *
 * @handle->handle_size indicate the space available to store the
 * variable part of the file handle in bytes. If there is not
 * enough space, the field is updated to return the minimum
 * value required.
 */
SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
		struct file_handle __user *, handle, int __user *, mnt_id,
		int, flag)
{
	struct path path;
	int lookup_flags;
	int err;

	if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
		return -EINVAL;

	lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
	if (flag & AT_EMPTY_PATH)
		lookup_flags |= LOOKUP_EMPTY;
	err = user_path_at(dfd, name, lookup_flags, &path);
	if (!err) {
		err = do_sys_name_to_handle(&path, handle, mnt_id);
		path_put(&path);
	}
	return err;
}

static struct vfsmount *get_vfsmount_from_fd(int fd)
{
	struct path path;

	if (fd == AT_FDCWD) {
		struct fs_struct *fs = current->fs;
		spin_lock(&fs->lock);
		path = fs->pwd;
		mntget(path.mnt);
		spin_unlock(&fs->lock);
	} else {
		int fput_needed;
		struct file *file = fget_light(fd, &fput_needed);
		if (!file)
			return ERR_PTR(-EBADF);
		path = file->f_path;
		mntget(path.mnt);
		fput_light(file, fput_needed);
	}
	return path.mnt;
}

static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
{
	return 1;
}

static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
			     struct path *path)
{
	int retval = 0;
	int handle_dwords;

	path->mnt = get_vfsmount_from_fd(mountdirfd);
	if (IS_ERR(path->mnt)) {
		retval = PTR_ERR(path->mnt);
		goto out_err;
	}
	/* change the handle size to multiple of sizeof(u32) */
	handle_dwords = handle->handle_bytes >> 2;
	path->dentry = exportfs_decode_fh(path->mnt,
					  (struct fid *)handle->f_handle,
					  handle_dwords, handle->handle_type,
					  vfs_dentry_acceptable, NULL);
	if (IS_ERR(path->dentry)) {
		retval = PTR_ERR(path->dentry);
		goto out_mnt;
	}
	return 0;
out_mnt:
	mntput(path->mnt);
out_err:
	return retval;
}

static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
		   struct path *path)
{
	int retval = 0;
	struct file_handle f_handle;
	struct file_handle *handle = NULL;

	/*
	 * With handle we don't look at the execute bit on the
	 * the directory. Ideally we would like CAP_DAC_SEARCH.
	 * But we don't have that
	 */
	if (!capable(CAP_DAC_READ_SEARCH)) {
		retval = -EPERM;
		goto out_err;
	}
	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
		retval = -EFAULT;
		goto out_err;
	}
	if ((f_handle.handle_bytes > MAX_HANDLE_SZ) ||
	    (f_handle.handle_bytes == 0)) {
		retval = -EINVAL;
		goto out_err;
	}
	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
			 GFP_KERNEL);
	if (!handle) {
		retval = -ENOMEM;
		goto out_err;
	}
	/* copy the full handle */
	if (copy_from_user(handle, ufh,
			   sizeof(struct file_handle) +
			   f_handle.handle_bytes)) {
		retval = -EFAULT;
		goto out_handle;
	}

	retval = do_handle_to_path(mountdirfd, handle, path);

out_handle:
	kfree(handle);
out_err:
	return retval;
}

long do_handle_open(int mountdirfd,
		    struct file_handle __user *ufh, int open_flag)
{
	long retval = 0;
	struct path path;
	struct file *file;
	int fd;

	retval = handle_to_path(mountdirfd, ufh, &path);
	if (retval)
		return retval;

	fd = get_unused_fd_flags(open_flag);
	if (fd < 0) {
		path_put(&path);
		return fd;
	}
	file = file_open_root(path.dentry, path.mnt, "", open_flag);
	if (IS_ERR(file)) {
		put_unused_fd(fd);
		retval =  PTR_ERR(file);
	} else {
		retval = fd;
		fsnotify_open(file);
		fd_install(fd, file);
	}
	path_put(&path);
	return retval;
}

/**
 * sys_open_by_handle_at: Open the file handle
 * @mountdirfd: directory file descriptor
 * @handle: file handle to be opened
 * @flag: open flags.
 *
 * @mountdirfd indicate the directory file descriptor
 * of the mount point. file handle is decoded relative
 * to the vfsmount pointed by the @mountdirfd. @flags
 * value is same as the open(2) flags.
 */
SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
		struct file_handle __user *, handle,
		int, flags)
{
	long ret;

	if (force_o_largefile())
		flags |= O_LARGEFILE;

	ret = do_handle_open(mountdirfd, handle, flags);
	return ret;
}
Commit	Line	Data
990d6c2d AK	1	#include <linux/syscalls.h>
	2	#include <linux/slab.h>
	3	#include <linux/fs.h>
	4	#include <linux/file.h>
	5	#include <linux/mount.h>
	6	#include <linux/namei.h>
	7	#include <linux/exportfs.h>
becfd1f3 AK	8	#include <linux/fs_struct.h>
becfd1f3 AK	9	#include <linux/fsnotify.h>
990d6c2d AK	10	#include <asm/uaccess.h>
	11	#include "internal.h"
	12
	13	static long do_sys_name_to_handle(struct path *path,
	14	struct file_handle __user *ufh,
	15	int __user *mnt_id)
	16	{
	17	long retval;
	18	struct file_handle f_handle;
	19	int handle_dwords, handle_bytes;
	20	struct file_handle *handle = NULL;
	21
	22	/*
	23	* We need t make sure wether the file system
	24	* support decoding of the file handle
	25	*/
	26	if (!path->mnt->mnt_sb->s_export_op \|\|
	27	!path->mnt->mnt_sb->s_export_op->fh_to_dentry)
	28	return -EOPNOTSUPP;
	29
	30	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
	31	return -EFAULT;
	32
	33	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
	34	return -EINVAL;
	35
	36	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
	37	GFP_KERNEL);
	38	if (!handle)
	39	return -ENOMEM;
	40
	41	/* convert handle size to multiple of sizeof(u32) */
	42	handle_dwords = f_handle.handle_bytes >> 2;
	43
	44	/* we ask for a non connected handle */
	45	retval = exportfs_encode_fh(path->dentry,
	46	(struct fid *)handle->f_handle,
	47	&handle_dwords, 0);
	48	handle->handle_type = retval;
	49	/* convert handle size to bytes */
	50	handle_bytes = handle_dwords * sizeof(u32);
	51	handle->handle_bytes = handle_bytes;
	52	if ((handle->handle_bytes > f_handle.handle_bytes) \|\|
	53	(retval == 255) \|\| (retval == -ENOSPC)) {
	54	/* As per old exportfs_encode_fh documentation
	55	* we could return ENOSPC to indicate overflow
	56	* But file system returned 255 always. So handle
	57	* both the values
	58	*/
	59	/*
	60	* set the handle size to zero so we copy only
	61	* non variable part of the file_handle
	62	*/
	63	handle_bytes = 0;
	64	retval = -EOVERFLOW;
	65	} else
	66	retval = 0;
	67	/* copy the mount id */
	68	if (copy_to_user(mnt_id, &path->mnt->mnt_id, sizeof(*mnt_id)) \|\|
	69	copy_to_user(ufh, handle,
	70	sizeof(struct file_handle) + handle_bytes))
	71	retval = -EFAULT;
	72	kfree(handle);
	73	return retval;
74	}
75
76	/**
77	* sys_name_to_handle_at: convert name to handle
78	* @dfd: directory relative to which name is interpreted if not absolute
79	* @name: name that should be converted to handle.
80	* @handle: resulting file handle
81	* @mnt_id: mount id of the file system containing the file
82	* @flag: flag value to indicate whether to follow symlink or not
83	*
84	* @handle->handle_size indicate the space available to store the
85	* variable part of the file handle in bytes. If there is not
86	* enough space, the field is updated to return the minimum
87	* value required.
88	*/
89	SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
90	struct file_handle __user , handle, int __user , mnt_id,
91	int, flag)
92	{
93	struct path path;
94	int lookup_flags;
95	int err;
96
97	if ((flag & ~(AT_SYMLINK_FOLLOW \| AT_EMPTY_PATH)) != 0)
98	return -EINVAL;
99
100	lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
101	if (flag & AT_EMPTY_PATH)
102	lookup_flags \|= LOOKUP_EMPTY;
103	err = user_path_at(dfd, name, lookup_flags, &path);
104	if (!err) {
105	err = do_sys_name_to_handle(&path, handle, mnt_id);
106	path_put(&path);
107	}
108	return err;
109	}
becfd1f3 AK	110
	111	static struct vfsmount *get_vfsmount_from_fd(int fd)
	112	{
	113	struct path path;
	114
	115	if (fd == AT_FDCWD) {
	116	struct fs_struct *fs = current->fs;
	117	spin_lock(&fs->lock);
	118	path = fs->pwd;
	119	mntget(path.mnt);
	120	spin_unlock(&fs->lock);
	121	} else {
	122	int fput_needed;
	123	struct file *file = fget_light(fd, &fput_needed);
	124	if (!file)
	125	return ERR_PTR(-EBADF);
	126	path = file->f_path;
	127	mntget(path.mnt);
	128	fput_light(file, fput_needed);
	129	}
	130	return path.mnt;
	131	}
	132
	133	static int vfs_dentry_acceptable(void context, struct dentry dentry)
	134	{
	135	return 1;
	136	}
	137
	138	static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
	139	struct path *path)
	140	{
	141	int retval = 0;
	142	int handle_dwords;
	143
	144	path->mnt = get_vfsmount_from_fd(mountdirfd);
	145	if (IS_ERR(path->mnt)) {
	146	retval = PTR_ERR(path->mnt);
	147	goto out_err;
	148	}
	149	/* change the handle size to multiple of sizeof(u32) */
	150	handle_dwords = handle->handle_bytes >> 2;
	151	path->dentry = exportfs_decode_fh(path->mnt,
	152	(struct fid *)handle->f_handle,
	153	handle_dwords, handle->handle_type,
	154	vfs_dentry_acceptable, NULL);
	155	if (IS_ERR(path->dentry)) {
	156	retval = PTR_ERR(path->dentry);
	157	goto out_mnt;
	158	}
	159	return 0;
	160	out_mnt:
	161	mntput(path->mnt);
	162	out_err:
	163	return retval;
	164	}
	165
	166	static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
	167	struct path *path)
	168	{
	169	int retval = 0;
	170	struct file_handle f_handle;
	171	struct file_handle *handle = NULL;
	172
	173	/*
174	* With handle we don't look at the execute bit on the
175	* the directory. Ideally we would like CAP_DAC_SEARCH.
176	* But we don't have that
177	*/
178	if (!capable(CAP_DAC_READ_SEARCH)) {
179	retval = -EPERM;
180	goto out_err;
181	}
182	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
183	retval = -EFAULT;
184	goto out_err;
185	}
186	if ((f_handle.handle_bytes > MAX_HANDLE_SZ) \|\|
187	(f_handle.handle_bytes == 0)) {
188	retval = -EINVAL;
189	goto out_err;
190	}
191	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
192	GFP_KERNEL);
193	if (!handle) {
194	retval = -ENOMEM;
195	goto out_err;
196	}
197	/* copy the full handle */
198	if (copy_from_user(handle, ufh,
199	sizeof(struct file_handle) +
200	f_handle.handle_bytes)) {
201	retval = -EFAULT;
202	goto out_handle;
203	}
204
205	retval = do_handle_to_path(mountdirfd, handle, path);
206
207	out_handle:
208	kfree(handle);
209	out_err:
210	return retval;
211	}
212
213	long do_handle_open(int mountdirfd,
214	struct file_handle __user *ufh, int open_flag)
215	{
216	long retval = 0;
217	struct path path;
218	struct file *file;
219	int fd;
220
221	retval = handle_to_path(mountdirfd, ufh, &path);
222	if (retval)
223	return retval;
224
225	fd = get_unused_fd_flags(open_flag);
226	if (fd < 0) {
227	path_put(&path);
228	return fd;
229	}
230	file = file_open_root(path.dentry, path.mnt, "", open_flag);
231	if (IS_ERR(file)) {
232	put_unused_fd(fd);
233	retval = PTR_ERR(file);
234	} else {
235	retval = fd;
236	fsnotify_open(file);
237	fd_install(fd, file);
238	}
239	path_put(&path);
240	return retval;
241	}
242
243	/**
244	* sys_open_by_handle_at: Open the file handle
245	* @mountdirfd: directory file descriptor
246	* @handle: file handle to be opened
247	* @flag: open flags.
248	*
249	* @mountdirfd indicate the directory file descriptor
250	* of the mount point. file handle is decoded relative
251	* to the vfsmount pointed by the @mountdirfd. @flags
252	* value is same as the open(2) flags.
253	*/
254	SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
255	struct file_handle __user *, handle,
256	int, flags)
257	{
258	long ret;
259
260	if (force_o_largefile())
261	flags \|= O_LARGEFILE;
262
263	ret = do_handle_open(mountdirfd, handle, flags);
264	return ret;
265	}