Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
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>
9 : #include <linux/fs_struct.h>
10 : #include <linux/fsnotify.h>
11 : #include <linux/personality.h>
12 : #include <linux/uaccess.h>
13 : #include <linux/compat.h>
14 : #include "internal.h"
15 : #include "mount.h"
16 :
17 0 : static long do_sys_name_to_handle(const struct path *path,
18 : struct file_handle __user *ufh,
19 : int __user *mnt_id, int fh_flags)
20 : {
21 : long retval;
22 : struct file_handle f_handle;
23 : int handle_dwords, handle_bytes;
24 0 : struct file_handle *handle = NULL;
25 :
26 : /*
27 : * We need to make sure whether the file system support decoding of
28 : * the file handle if decodeable file handle was requested.
29 : * Otherwise, even empty export_operations are sufficient to opt-in
30 : * to encoding FIDs.
31 : */
32 0 : if (!path->dentry->d_sb->s_export_op ||
33 0 : (!(fh_flags & EXPORT_FH_FID) &&
34 0 : !path->dentry->d_sb->s_export_op->fh_to_dentry))
35 : return -EOPNOTSUPP;
36 :
37 0 : if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
38 : return -EFAULT;
39 :
40 0 : if (f_handle.handle_bytes > MAX_HANDLE_SZ)
41 : return -EINVAL;
42 :
43 0 : handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
44 : GFP_KERNEL);
45 0 : if (!handle)
46 : return -ENOMEM;
47 :
48 : /* convert handle size to multiple of sizeof(u32) */
49 0 : handle_dwords = f_handle.handle_bytes >> 2;
50 :
51 : /* we ask for a non connectable maybe decodeable file handle */
52 0 : retval = exportfs_encode_fh(path->dentry,
53 0 : (struct fid *)handle->f_handle,
54 : &handle_dwords, fh_flags);
55 0 : handle->handle_type = retval;
56 : /* convert handle size to bytes */
57 0 : handle_bytes = handle_dwords * sizeof(u32);
58 0 : handle->handle_bytes = handle_bytes;
59 0 : if ((handle->handle_bytes > f_handle.handle_bytes) ||
60 0 : (retval == FILEID_INVALID) || (retval < 0)) {
61 : /* As per old exportfs_encode_fh documentation
62 : * we could return ENOSPC to indicate overflow
63 : * But file system returned 255 always. So handle
64 : * both the values
65 : */
66 0 : if (retval == FILEID_INVALID || retval == -ENOSPC)
67 0 : retval = -EOVERFLOW;
68 : /*
69 : * set the handle size to zero so we copy only
70 : * non variable part of the file_handle
71 : */
72 : handle_bytes = 0;
73 : } else
74 : retval = 0;
75 : /* copy the mount id */
76 0 : if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) ||
77 0 : copy_to_user(ufh, handle,
78 : sizeof(struct file_handle) + handle_bytes))
79 : retval = -EFAULT;
80 0 : kfree(handle);
81 0 : return retval;
82 : }
83 :
84 : /**
85 : * sys_name_to_handle_at: convert name to handle
86 : * @dfd: directory relative to which name is interpreted if not absolute
87 : * @name: name that should be converted to handle.
88 : * @handle: resulting file handle
89 : * @mnt_id: mount id of the file system containing the file
90 : * @flag: flag value to indicate whether to follow symlink or not
91 : * and whether a decodable file handle is required.
92 : *
93 : * @handle->handle_size indicate the space available to store the
94 : * variable part of the file handle in bytes. If there is not
95 : * enough space, the field is updated to return the minimum
96 : * value required.
97 : */
98 0 : SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
99 : struct file_handle __user *, handle, int __user *, mnt_id,
100 : int, flag)
101 : {
102 : struct path path;
103 : int lookup_flags;
104 : int fh_flags;
105 : int err;
106 :
107 0 : if (flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH | AT_HANDLE_FID))
108 : return -EINVAL;
109 :
110 0 : lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
111 0 : fh_flags = (flag & AT_HANDLE_FID) ? EXPORT_FH_FID : 0;
112 0 : if (flag & AT_EMPTY_PATH)
113 0 : lookup_flags |= LOOKUP_EMPTY;
114 0 : err = user_path_at(dfd, name, lookup_flags, &path);
115 0 : if (!err) {
116 0 : err = do_sys_name_to_handle(&path, handle, mnt_id, fh_flags);
117 0 : path_put(&path);
118 : }
119 0 : return err;
120 : }
121 :
122 0 : static struct vfsmount *get_vfsmount_from_fd(int fd)
123 : {
124 : struct vfsmount *mnt;
125 :
126 0 : if (fd == AT_FDCWD) {
127 0 : struct fs_struct *fs = current->fs;
128 0 : spin_lock(&fs->lock);
129 0 : mnt = mntget(fs->pwd.mnt);
130 0 : spin_unlock(&fs->lock);
131 : } else {
132 0 : struct fd f = fdget(fd);
133 0 : if (!f.file)
134 0 : return ERR_PTR(-EBADF);
135 0 : mnt = mntget(f.file->f_path.mnt);
136 0 : fdput(f);
137 : }
138 : return mnt;
139 : }
140 :
141 0 : static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
142 : {
143 0 : return 1;
144 : }
145 :
146 0 : static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
147 : struct path *path)
148 : {
149 0 : int retval = 0;
150 : int handle_dwords;
151 :
152 0 : path->mnt = get_vfsmount_from_fd(mountdirfd);
153 0 : if (IS_ERR(path->mnt)) {
154 0 : retval = PTR_ERR(path->mnt);
155 0 : goto out_err;
156 : }
157 : /* change the handle size to multiple of sizeof(u32) */
158 0 : handle_dwords = handle->handle_bytes >> 2;
159 0 : path->dentry = exportfs_decode_fh(path->mnt,
160 0 : (struct fid *)handle->f_handle,
161 : handle_dwords, handle->handle_type,
162 : vfs_dentry_acceptable, NULL);
163 0 : if (IS_ERR(path->dentry)) {
164 0 : retval = PTR_ERR(path->dentry);
165 : goto out_mnt;
166 : }
167 : return 0;
168 : out_mnt:
169 0 : mntput(path->mnt);
170 : out_err:
171 : return retval;
172 : }
173 :
174 0 : static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
175 : struct path *path)
176 : {
177 0 : int retval = 0;
178 : struct file_handle f_handle;
179 0 : struct file_handle *handle = NULL;
180 :
181 : /*
182 : * With handle we don't look at the execute bit on the
183 : * directory. Ideally we would like CAP_DAC_SEARCH.
184 : * But we don't have that
185 : */
186 0 : if (!capable(CAP_DAC_READ_SEARCH)) {
187 : retval = -EPERM;
188 : goto out_err;
189 : }
190 0 : if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
191 : retval = -EFAULT;
192 : goto out_err;
193 : }
194 0 : if ((f_handle.handle_bytes > MAX_HANDLE_SZ) ||
195 : (f_handle.handle_bytes == 0)) {
196 : retval = -EINVAL;
197 : goto out_err;
198 : }
199 0 : handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
200 : GFP_KERNEL);
201 0 : if (!handle) {
202 : retval = -ENOMEM;
203 : goto out_err;
204 : }
205 : /* copy the full handle */
206 0 : *handle = f_handle;
207 0 : if (copy_from_user(&handle->f_handle,
208 0 : &ufh->f_handle,
209 0 : f_handle.handle_bytes)) {
210 : retval = -EFAULT;
211 : goto out_handle;
212 : }
213 :
214 0 : retval = do_handle_to_path(mountdirfd, handle, path);
215 :
216 : out_handle:
217 0 : kfree(handle);
218 : out_err:
219 0 : return retval;
220 : }
221 :
222 0 : static long do_handle_open(int mountdirfd, struct file_handle __user *ufh,
223 : int open_flag)
224 : {
225 0 : long retval = 0;
226 : struct path path;
227 : struct file *file;
228 : int fd;
229 :
230 0 : retval = handle_to_path(mountdirfd, ufh, &path);
231 0 : if (retval)
232 : return retval;
233 :
234 0 : fd = get_unused_fd_flags(open_flag);
235 0 : if (fd < 0) {
236 0 : path_put(&path);
237 0 : return fd;
238 : }
239 0 : file = file_open_root(&path, "", open_flag, 0);
240 0 : if (IS_ERR(file)) {
241 0 : put_unused_fd(fd);
242 0 : retval = PTR_ERR(file);
243 : } else {
244 0 : retval = fd;
245 0 : fd_install(fd, file);
246 : }
247 0 : path_put(&path);
248 0 : return retval;
249 : }
250 :
251 : /**
252 : * sys_open_by_handle_at: Open the file handle
253 : * @mountdirfd: directory file descriptor
254 : * @handle: file handle to be opened
255 : * @flags: open flags.
256 : *
257 : * @mountdirfd indicate the directory file descriptor
258 : * of the mount point. file handle is decoded relative
259 : * to the vfsmount pointed by the @mountdirfd. @flags
260 : * value is same as the open(2) flags.
261 : */
262 0 : SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
263 : struct file_handle __user *, handle,
264 : int, flags)
265 : {
266 : long ret;
267 :
268 : if (force_o_largefile())
269 0 : flags |= O_LARGEFILE;
270 :
271 0 : ret = do_handle_open(mountdirfd, handle, flags);
272 : return ret;
273 : }
274 :
275 : #ifdef CONFIG_COMPAT
276 : /*
277 : * Exactly like fs/open.c:sys_open_by_handle_at(), except that it
278 : * doesn't set the O_LARGEFILE flag.
279 : */
280 : COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
281 : struct file_handle __user *, handle, int, flags)
282 : {
283 : return do_handle_open(mountdirfd, handle, flags);
284 : }
285 : #endif
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