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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 | |
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 | /* |
25 | * We need t make sure wether 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 == 255) || (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 | */ |
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 | } |
113 | |
114 | static struct vfsmount *get_vfsmount_from_fd(int fd) |
115 | { |
116 | struct path path; |
117 | |
118 | if (fd == AT_FDCWD) { |
119 | struct fs_struct *fs = current->fs; |
120 | spin_lock(&fs->lock); |
121 | path = fs->pwd; |
122 | mntget(path.mnt); |
123 | spin_unlock(&fs->lock); |
124 | } else { |
125 | int fput_needed; |
126 | struct file *file = fget_light(fd, &fput_needed); |
127 | if (!file) |
128 | return ERR_PTR(-EBADF); |
129 | path = file->f_path; |
130 | mntget(path.mnt); |
131 | fput_light(file, fput_needed); |
132 | } |
133 | return path.mnt; |
134 | } |
135 | |
136 | static int vfs_dentry_acceptable(void *context, struct dentry *dentry) |
137 | { |
138 | return 1; |
139 | } |
140 | |
141 | static int do_handle_to_path(int mountdirfd, struct file_handle *handle, |
142 | struct path *path) |
143 | { |
144 | int retval = 0; |
145 | int handle_dwords; |
146 | |
147 | path->mnt = get_vfsmount_from_fd(mountdirfd); |
148 | if (IS_ERR(path->mnt)) { |
149 | retval = PTR_ERR(path->mnt); |
150 | goto out_err; |
151 | } |
152 | /* change the handle size to multiple of sizeof(u32) */ |
153 | handle_dwords = handle->handle_bytes >> 2; |
154 | path->dentry = exportfs_decode_fh(path->mnt, |
155 | (struct fid *)handle->f_handle, |
156 | handle_dwords, handle->handle_type, |
157 | vfs_dentry_acceptable, NULL); |
158 | if (IS_ERR(path->dentry)) { |
159 | retval = PTR_ERR(path->dentry); |
160 | goto out_mnt; |
161 | } |
162 | return 0; |
163 | out_mnt: |
164 | mntput(path->mnt); |
165 | out_err: |
166 | return retval; |
167 | } |
168 | |
169 | static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, |
170 | struct path *path) |
171 | { |
172 | int retval = 0; |
173 | struct file_handle f_handle; |
174 | struct file_handle *handle = NULL; |
175 | |
176 | /* |
177 | * With handle we don't look at the execute bit on the |
178 | * the directory. Ideally we would like CAP_DAC_SEARCH. |
179 | * But we don't have that |
180 | */ |
181 | if (!capable(CAP_DAC_READ_SEARCH)) { |
182 | retval = -EPERM; |
183 | goto out_err; |
184 | } |
185 | if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { |
186 | retval = -EFAULT; |
187 | goto out_err; |
188 | } |
189 | if ((f_handle.handle_bytes > MAX_HANDLE_SZ) || |
190 | (f_handle.handle_bytes == 0)) { |
191 | retval = -EINVAL; |
192 | goto out_err; |
193 | } |
194 | handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, |
195 | GFP_KERNEL); |
196 | if (!handle) { |
197 | retval = -ENOMEM; |
198 | goto out_err; |
199 | } |
200 | /* copy the full handle */ |
201 | if (copy_from_user(handle, ufh, |
202 | sizeof(struct file_handle) + |
203 | f_handle.handle_bytes)) { |
204 | retval = -EFAULT; |
205 | goto out_handle; |
206 | } |
207 | |
208 | retval = do_handle_to_path(mountdirfd, handle, path); |
209 | |
210 | out_handle: |
211 | kfree(handle); |
212 | out_err: |
213 | return retval; |
214 | } |
215 | |
216 | long do_handle_open(int mountdirfd, |
217 | struct file_handle __user *ufh, int open_flag) |
218 | { |
219 | long retval = 0; |
220 | struct path path; |
221 | struct file *file; |
222 | int fd; |
223 | |
224 | retval = handle_to_path(mountdirfd, ufh, &path); |
225 | if (retval) |
226 | return retval; |
227 | |
228 | fd = get_unused_fd_flags(open_flag); |
229 | if (fd < 0) { |
230 | path_put(&path); |
231 | return fd; |
232 | } |
233 | file = file_open_root(path.dentry, path.mnt, "", open_flag); |
234 | if (IS_ERR(file)) { |
235 | put_unused_fd(fd); |
236 | retval = PTR_ERR(file); |
237 | } else { |
238 | retval = fd; |
239 | fsnotify_open(file); |
240 | fd_install(fd, file); |
241 | } |
242 | path_put(&path); |
243 | return retval; |
244 | } |
245 | |
246 | /** |
247 | * sys_open_by_handle_at: Open the file handle |
248 | * @mountdirfd: directory file descriptor |
249 | * @handle: file handle to be opened |
250 | * @flag: open flags. |
251 | * |
252 | * @mountdirfd indicate the directory file descriptor |
253 | * of the mount point. file handle is decoded relative |
254 | * to the vfsmount pointed by the @mountdirfd. @flags |
255 | * value is same as the open(2) flags. |
256 | */ |
257 | SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd, |
258 | struct file_handle __user *, handle, |
259 | int, flags) |
260 | { |
261 | long ret; |
262 | |
263 | if (force_o_largefile()) |
264 | flags |= O_LARGEFILE; |
265 | |
266 | ret = do_handle_open(mountdirfd, handle, flags); |
267 | return ret; |
268 | } |
269 |
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Tags:
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