[mirror_ubuntu-bionic-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 <linux/personality.h>
#include <linux/uaccess.h>
#include "internal.h"
#include "mount.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 to make sure whether the file system
	 * support decoding of the file handle
	 */
	if (!path->dentry->d_sb->s_export_op ||
	    !path->dentry->d_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 == FILEID_INVALID) || (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, &real_mount(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 vfsmount *mnt;

	if (fd == AT_FDCWD) {
		struct fs_struct *fs = current->fs;
		spin_lock(&fs->lock);
		mnt = mntget(fs->pwd.mnt);
		spin_unlock(&fs->lock);
	} else {
		struct fd f = fdget(fd);
		if (!f.file)
			return ERR_PTR(-EBADF);
		mnt = mntget(f.file->f_path.mnt);
		fdput(f);
	}
	return 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 */
	*handle = f_handle;
	if (copy_from_user(&handle->f_handle,
			   &ufh->f_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, 0);
	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>
ed5afeaf	10	#include <linux/personality.h>
7c0f6ba6	11	#include <linux/uaccess.h>
990d6c2d	12	#include "internal.h"
15169fe7	13	#include "mount.h"
990d6c2d AK	14
	15	static long do_sys_name_to_handle(struct path *path,
	16	struct file_handle __user *ufh,
	17	int __user *mnt_id)
	18	{
	19	long retval;
	20	struct file_handle f_handle;
	21	int handle_dwords, handle_bytes;
	22	struct file_handle *handle = NULL;
	23
	24	/*
48fc7f7e	25	* We need to make sure whether the file system
990d6c2d AK	26	* support decoding of the file handle
990d6c2d AK	27	*/
d8c9584e AV	28	if (!path->dentry->d_sb->s_export_op \|\|
d8c9584e AV	29	!path->dentry->d_sb->s_export_op->fh_to_dentry)
990d6c2d AK	30	return -EOPNOTSUPP;
	31
	32	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
	33	return -EFAULT;
	34
	35	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
	36	return -EINVAL;
	37
	38	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
	39	GFP_KERNEL);
	40	if (!handle)
	41	return -ENOMEM;
	42
48fc7f7e	43	/* convert handle size to multiple of sizeof(u32) */
990d6c2d AK	44	handle_dwords = f_handle.handle_bytes >> 2;
	45
	46	/* we ask for a non connected handle */
	47	retval = exportfs_encode_fh(path->dentry,
	48	(struct fid *)handle->f_handle,
	49	&handle_dwords, 0);
	50	handle->handle_type = retval;
	51	/* convert handle size to bytes */
	52	handle_bytes = handle_dwords * sizeof(u32);
	53	handle->handle_bytes = handle_bytes;
	54	if ((handle->handle_bytes > f_handle.handle_bytes) \|\|
216b6cbd	55	(retval == FILEID_INVALID) \|\| (retval == -ENOSPC)) {
990d6c2d AK	56	/* As per old exportfs_encode_fh documentation
	57	* we could return ENOSPC to indicate overflow
	58	* But file system returned 255 always. So handle
	59	* both the values
	60	*/
	61	/*
	62	* set the handle size to zero so we copy only
	63	* non variable part of the file_handle
	64	*/
	65	handle_bytes = 0;
	66	retval = -EOVERFLOW;
	67	} else
	68	retval = 0;
	69	/* copy the mount id */
15169fe7 AV	70	if (copy_to_user(mnt_id, &real_mount(path->mnt)->mnt_id,
15169fe7 AV	71	sizeof(*mnt_id)) \|\|
990d6c2d AK	72	copy_to_user(ufh, handle,
	73	sizeof(struct file_handle) + handle_bytes))
	74	retval = -EFAULT;
	75	kfree(handle);
	76	return retval;
	77	}
	78
	79	/**
	80	* sys_name_to_handle_at: convert name to handle
	81	* @dfd: directory relative to which name is interpreted if not absolute
	82	* @name: name that should be converted to handle.
	83	* @handle: resulting file handle
	84	* @mnt_id: mount id of the file system containing the file
	85	* @flag: flag value to indicate whether to follow symlink or not
	86	*
	87	* @handle->handle_size indicate the space available to store the
	88	* variable part of the file handle in bytes. If there is not
	89	* enough space, the field is updated to return the minimum
	90	* value required.
	91	*/
	92	SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
	93	struct file_handle __user , handle, int __user , mnt_id,
	94	int, flag)
	95	{
	96	struct path path;
	97	int lookup_flags;
	98	int err;
	99
	100	if ((flag & ~(AT_SYMLINK_FOLLOW \| AT_EMPTY_PATH)) != 0)
	101	return -EINVAL;
	102
	103	lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
	104	if (flag & AT_EMPTY_PATH)
	105	lookup_flags \|= LOOKUP_EMPTY;
	106	err = user_path_at(dfd, name, lookup_flags, &path);
	107	if (!err) {
	108	err = do_sys_name_to_handle(&path, handle, mnt_id);
	109	path_put(&path);
	110	}
	111	return err;
	112	}
becfd1f3 AK	113
	114	static struct vfsmount *get_vfsmount_from_fd(int fd)
	115	{
2903ff01	116	struct vfsmount *mnt;
becfd1f3 AK	117
	118	if (fd == AT_FDCWD) {
	119	struct fs_struct *fs = current->fs;
	120	spin_lock(&fs->lock);
2903ff01	121	mnt = mntget(fs->pwd.mnt);
becfd1f3 AK	122	spin_unlock(&fs->lock);
becfd1f3 AK	123	} else {
2903ff01 AV	124	struct fd f = fdget(fd);
2903ff01 AV	125	if (!f.file)
becfd1f3	126	return ERR_PTR(-EBADF);
2903ff01 AV	127	mnt = mntget(f.file->f_path.mnt);
2903ff01 AV	128	fdput(f);
becfd1f3	129	}
2903ff01	130	return mnt;
becfd1f3 AK	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 */
161f873b SL	198	*handle = f_handle;
	199	if (copy_from_user(&handle->f_handle,
	200	&ufh->f_handle,
becfd1f3 AK	201	f_handle.handle_bytes)) {
	202	retval = -EFAULT;
	203	goto out_handle;
	204	}
	205
	206	retval = do_handle_to_path(mountdirfd, handle, path);
	207
	208	out_handle:
	209	kfree(handle);
	210	out_err:
	211	return retval;
	212	}
	213
	214	long do_handle_open(int mountdirfd,
	215	struct file_handle __user *ufh, int open_flag)
	216	{
	217	long retval = 0;
	218	struct path path;
	219	struct file *file;
	220	int fd;
	221
	222	retval = handle_to_path(mountdirfd, ufh, &path);
	223	if (retval)
	224	return retval;
	225
	226	fd = get_unused_fd_flags(open_flag);
	227	if (fd < 0) {
	228	path_put(&path);
	229	return fd;
	230	}
378c6520	231	file = file_open_root(path.dentry, path.mnt, "", open_flag, 0);
becfd1f3 AK	232	if (IS_ERR(file)) {
	233	put_unused_fd(fd);
	234	retval = PTR_ERR(file);
	235	} else {
	236	retval = fd;
	237	fsnotify_open(file);
	238	fd_install(fd, file);
	239	}
	240	path_put(&path);
	241	return retval;
	242	}
	243
	244	/**
	245	* sys_open_by_handle_at: Open the file handle
	246	* @mountdirfd: directory file descriptor
	247	* @handle: file handle to be opened
	248	* @flag: open flags.
	249	*
	250	* @mountdirfd indicate the directory file descriptor
	251	* of the mount point. file handle is decoded relative
	252	* to the vfsmount pointed by the @mountdirfd. @flags
	253	* value is same as the open(2) flags.
	254	*/
	255	SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
	256	struct file_handle __user *, handle,
	257	int, flags)
	258	{
	259	long ret;
	260
	261	if (force_o_largefile())
	262	flags \|= O_LARGEFILE;
	263
	264	ret = do_handle_open(mountdirfd, handle, flags);
	265	return ret;
	266	}