[linux.git] / fs / fhandle.c

// SPDX-License-Identifier: GPL-2.0
#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 <linux/compat.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 (put_user(real_mount(path->mnt)->mnt_id, 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;
}

static 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;
}

#ifdef CONFIG_COMPAT
/*
 * Exactly like fs/open.c:sys_open_by_handle_at(), except that it
 * doesn't set the O_LARGEFILE flag.
 */
COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
			     struct file_handle __user *, handle, int, flags)
{
	return do_handle_open(mountdirfd, handle, flags);
}
#endif
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
990d6c2d AK	2	#include <linux/syscalls.h>
	3	#include <linux/slab.h>
	4	#include <linux/fs.h>
	5	#include <linux/file.h>
	6	#include <linux/mount.h>
	7	#include <linux/namei.h>
	8	#include <linux/exportfs.h>
becfd1f3 AK	9	#include <linux/fs_struct.h>
becfd1f3 AK	10	#include <linux/fsnotify.h>
ed5afeaf	11	#include <linux/personality.h>
7c0f6ba6	12	#include <linux/uaccess.h>
2b891026	13	#include <linux/compat.h>
990d6c2d	14	#include "internal.h"
15169fe7	15	#include "mount.h"
990d6c2d AK	16
	17	static long do_sys_name_to_handle(struct path *path,
	18	struct file_handle __user *ufh,
	19	int __user *mnt_id)
	20	{
	21	long retval;
	22	struct file_handle f_handle;
	23	int handle_dwords, handle_bytes;
	24	struct file_handle *handle = NULL;
	25
	26	/*
48fc7f7e	27	* We need to make sure whether the file system
990d6c2d AK	28	* support decoding of the file handle
990d6c2d AK	29	*/
d8c9584e AV	30	if (!path->dentry->d_sb->s_export_op \|\|
d8c9584e AV	31	!path->dentry->d_sb->s_export_op->fh_to_dentry)
990d6c2d AK	32	return -EOPNOTSUPP;
	33
	34	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
	35	return -EFAULT;
	36
	37	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
	38	return -EINVAL;
	39
	40	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
	41	GFP_KERNEL);
	42	if (!handle)
	43	return -ENOMEM;
	44
48fc7f7e	45	/* convert handle size to multiple of sizeof(u32) */
990d6c2d AK	46	handle_dwords = f_handle.handle_bytes >> 2;
	47
	48	/* we ask for a non connected handle */
	49	retval = exportfs_encode_fh(path->dentry,
	50	(struct fid *)handle->f_handle,
	51	&handle_dwords, 0);
	52	handle->handle_type = retval;
	53	/* convert handle size to bytes */
	54	handle_bytes = handle_dwords * sizeof(u32);
	55	handle->handle_bytes = handle_bytes;
	56	if ((handle->handle_bytes > f_handle.handle_bytes) \|\|
216b6cbd	57	(retval == FILEID_INVALID) \|\| (retval == -ENOSPC)) {
990d6c2d AK	58	/* As per old exportfs_encode_fh documentation
	59	* we could return ENOSPC to indicate overflow
	60	* But file system returned 255 always. So handle
	61	* both the values
	62	*/
	63	/*
	64	* set the handle size to zero so we copy only
	65	* non variable part of the file_handle
	66	*/
	67	handle_bytes = 0;
	68	retval = -EOVERFLOW;
	69	} else
	70	retval = 0;
	71	/* copy the mount id */
6391af6f	72	if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) \|\|
990d6c2d AK	73	copy_to_user(ufh, handle,
	74	sizeof(struct file_handle) + handle_bytes))
	75	retval = -EFAULT;
	76	kfree(handle);
	77	return retval;
	78	}
	79
	80	/**
	81	* sys_name_to_handle_at: convert name to handle
	82	* @dfd: directory relative to which name is interpreted if not absolute
	83	* @name: name that should be converted to handle.
	84	* @handle: resulting file handle
	85	* @mnt_id: mount id of the file system containing the file
	86	* @flag: flag value to indicate whether to follow symlink or not
	87	*
	88	* @handle->handle_size indicate the space available to store the
	89	* variable part of the file handle in bytes. If there is not
	90	* enough space, the field is updated to return the minimum
	91	* value required.
	92	*/
	93	SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
	94	struct file_handle __user , handle, int __user , mnt_id,
	95	int, flag)
	96	{
	97	struct path path;
	98	int lookup_flags;
	99	int err;
	100
	101	if ((flag & ~(AT_SYMLINK_FOLLOW \| AT_EMPTY_PATH)) != 0)
	102	return -EINVAL;
	103
	104	lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
	105	if (flag & AT_EMPTY_PATH)
	106	lookup_flags \|= LOOKUP_EMPTY;
	107	err = user_path_at(dfd, name, lookup_flags, &path);
	108	if (!err) {
	109	err = do_sys_name_to_handle(&path, handle, mnt_id);
	110	path_put(&path);
	111	}
	112	return err;
	113	}
becfd1f3 AK	114
	115	static struct vfsmount *get_vfsmount_from_fd(int fd)
	116	{
2903ff01	117	struct vfsmount *mnt;
becfd1f3 AK	118
	119	if (fd == AT_FDCWD) {
	120	struct fs_struct *fs = current->fs;
	121	spin_lock(&fs->lock);
2903ff01	122	mnt = mntget(fs->pwd.mnt);
becfd1f3 AK	123	spin_unlock(&fs->lock);
becfd1f3 AK	124	} else {
2903ff01 AV	125	struct fd f = fdget(fd);
2903ff01 AV	126	if (!f.file)
becfd1f3	127	return ERR_PTR(-EBADF);
2903ff01 AV	128	mnt = mntget(f.file->f_path.mnt);
2903ff01 AV	129	fdput(f);
becfd1f3	130	}
2903ff01	131	return mnt;
becfd1f3 AK	132	}
	133
	134	static int vfs_dentry_acceptable(void context, struct dentry dentry)
	135	{
	136	return 1;
	137	}
	138
	139	static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
	140	struct path *path)
	141	{
	142	int retval = 0;
	143	int handle_dwords;
	144
	145	path->mnt = get_vfsmount_from_fd(mountdirfd);
	146	if (IS_ERR(path->mnt)) {
	147	retval = PTR_ERR(path->mnt);
	148	goto out_err;
	149	}
	150	/* change the handle size to multiple of sizeof(u32) */
	151	handle_dwords = handle->handle_bytes >> 2;
	152	path->dentry = exportfs_decode_fh(path->mnt,
	153	(struct fid *)handle->f_handle,
	154	handle_dwords, handle->handle_type,
	155	vfs_dentry_acceptable, NULL);
	156	if (IS_ERR(path->dentry)) {
	157	retval = PTR_ERR(path->dentry);
	158	goto out_mnt;
	159	}
	160	return 0;
	161	out_mnt:
	162	mntput(path->mnt);
	163	out_err:
	164	return retval;
	165	}
	166
	167	static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
	168	struct path *path)
	169	{
	170	int retval = 0;
	171	struct file_handle f_handle;
	172	struct file_handle *handle = NULL;
	173
	174	/*
	175	* With handle we don't look at the execute bit on the
	176	* the directory. Ideally we would like CAP_DAC_SEARCH.
	177	* But we don't have that
	178	*/
	179	if (!capable(CAP_DAC_READ_SEARCH)) {
	180	retval = -EPERM;
	181	goto out_err;
	182	}
	183	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
	184	retval = -EFAULT;
	185	goto out_err;
	186	}
	187	if ((f_handle.handle_bytes > MAX_HANDLE_SZ) \|\|
	188	(f_handle.handle_bytes == 0)) {
	189	retval = -EINVAL;
	190	goto out_err;
	191	}
	192	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
	193	GFP_KERNEL);
	194	if (!handle) {
	195	retval = -ENOMEM;
196	goto out_err;
197	}
198	/* copy the full handle */
161f873b SL	199	*handle = f_handle;
	200	if (copy_from_user(&handle->f_handle,
	201	&ufh->f_handle,
becfd1f3 AK	202	f_handle.handle_bytes)) {
	203	retval = -EFAULT;
	204	goto out_handle;
	205	}
	206
	207	retval = do_handle_to_path(mountdirfd, handle, path);
	208
	209	out_handle:
	210	kfree(handle);
	211	out_err:
	212	return retval;
	213	}
	214
73ecf5cf AV	215	static long do_handle_open(int mountdirfd, struct file_handle __user *ufh,
73ecf5cf AV	216	int open_flag)
becfd1f3 AK	217	{
	218	long retval = 0;
	219	struct path path;
	220	struct file *file;
	221	int fd;
	222
	223	retval = handle_to_path(mountdirfd, ufh, &path);
	224	if (retval)
	225	return retval;
	226
	227	fd = get_unused_fd_flags(open_flag);
	228	if (fd < 0) {
	229	path_put(&path);
	230	return fd;
	231	}
378c6520	232	file = file_open_root(path.dentry, path.mnt, "", open_flag, 0);
becfd1f3 AK	233	if (IS_ERR(file)) {
	234	put_unused_fd(fd);
	235	retval = PTR_ERR(file);
	236	} else {
	237	retval = fd;
	238	fsnotify_open(file);
	239	fd_install(fd, file);
	240	}
	241	path_put(&path);
	242	return retval;
	243	}
	244
	245	/**
	246	* sys_open_by_handle_at: Open the file handle
	247	* @mountdirfd: directory file descriptor
	248	* @handle: file handle to be opened
	249	* @flag: open flags.
	250	*
	251	* @mountdirfd indicate the directory file descriptor
	252	* of the mount point. file handle is decoded relative
	253	* to the vfsmount pointed by the @mountdirfd. @flags
	254	* value is same as the open(2) flags.
	255	*/
	256	SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
	257	struct file_handle __user *, handle,
	258	int, flags)
	259	{
	260	long ret;
	261
	262	if (force_o_largefile())
	263	flags \|= O_LARGEFILE;
	264
	265	ret = do_handle_open(mountdirfd, handle, flags);
	266	return ret;
	267	}
2b891026 AV	268
	269	#ifdef CONFIG_COMPAT
	270	/*
	271	* Exactly like fs/open.c:sys_open_by_handle_at(), except that it
	272	* doesn't set the O_LARGEFILE flag.
	273	*/
	274	COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
	275	struct file_handle __user *, handle, int, flags)
	276	{
	277	return do_handle_open(mountdirfd, handle, flags);
	278	}
	279	#endif