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>
8#include <linux/fs_struct.h>
9#include <linux/fsnotify.h>
10#include <linux/personality.h>
11#include <asm/uaccess.h>
12#include "internal.h"
13#include "mount.h"
14
15static 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	/*
25	 * We need to make sure whether the file system
26	 * support decoding of the file handle
27	 */
28	if (!path->dentry->d_sb->s_export_op ||
29	    !path->dentry->d_sb->s_export_op->fh_to_dentry)
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
43	/* convert handle size to multiple of sizeof(u32) */
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) ||
55	    (retval == FILEID_INVALID) || (retval == -ENOSPC)) {
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 */
70	if (copy_to_user(mnt_id, &real_mount(path->mnt)->mnt_id,
71			 sizeof(*mnt_id)) ||
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 */
92SYSCALL_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}
113
114static struct vfsmount *get_vfsmount_from_fd(int fd)
115{
116	struct vfsmount *mnt;
117
118	if (fd == AT_FDCWD) {
119		struct fs_struct *fs = current->fs;
120		spin_lock(&fs->lock);
121		mnt = mntget(fs->pwd.mnt);
122		spin_unlock(&fs->lock);
123	} else {
124		struct fd f = fdget(fd);
125		if (!f.file)
126			return ERR_PTR(-EBADF);
127		mnt = mntget(f.file->f_path.mnt);
128		fdput(f);
129	}
130	return mnt;
131}
132
133static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
134{
135	return 1;
136}
137
138static 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;
160out_mnt:
161	mntput(path->mnt);
162out_err:
163	return retval;
164}
165
166static 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	*handle = f_handle;
199	if (copy_from_user(&handle->f_handle,
200			   &ufh->f_handle,
201			   f_handle.handle_bytes)) {
202		retval = -EFAULT;
203		goto out_handle;
204	}
205
206	retval = do_handle_to_path(mountdirfd, handle, path);
207
208out_handle:
209	kfree(handle);
210out_err:
211	return retval;
212}
213
214long 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	}
231	file = file_open_root(path.dentry, path.mnt, "", open_flag, 0);
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 */
255SYSCALL_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}
267