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-rw-r--r--fs/fhandle.c265
1 files changed, 265 insertions, 0 deletions
diff --git a/fs/fhandle.c b/fs/fhandle.c
new file mode 100644
index 000000000000..bf93ad2bee07
--- /dev/null
+++ b/fs/fhandle.c
@@ -0,0 +1,265 @@
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 <asm/uaccess.h>
11#include "internal.h"
12
13static long do_sys_name_to_handle(struct path *path,
14 struct file_handle __user *ufh,
15 int __user *mnt_id)
16{
17 long retval;
18 struct file_handle f_handle;
19 int handle_dwords, handle_bytes;
20 struct file_handle *handle = NULL;
21
22 /*
23 * We need t make sure wether the file system
24 * support decoding of the file handle
25 */
26 if (!path->mnt->mnt_sb->s_export_op ||
27 !path->mnt->mnt_sb->s_export_op->fh_to_dentry)
28 return -EOPNOTSUPP;
29
30 if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
31 return -EFAULT;
32
33 if (f_handle.handle_bytes > MAX_HANDLE_SZ)
34 return -EINVAL;
35
36 handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
37 GFP_KERNEL);
38 if (!handle)
39 return -ENOMEM;
40
41 /* convert handle size to multiple of sizeof(u32) */
42 handle_dwords = f_handle.handle_bytes >> 2;
43
44 /* we ask for a non connected handle */
45 retval = exportfs_encode_fh(path->dentry,
46 (struct fid *)handle->f_handle,
47 &handle_dwords, 0);
48 handle->handle_type = retval;
49 /* convert handle size to bytes */
50 handle_bytes = handle_dwords * sizeof(u32);
51 handle->handle_bytes = handle_bytes;
52 if ((handle->handle_bytes > f_handle.handle_bytes) ||
53 (retval == 255) || (retval == -ENOSPC)) {
54 /* As per old exportfs_encode_fh documentation
55 * we could return ENOSPC to indicate overflow
56 * But file system returned 255 always. So handle
57 * both the values
58 */
59 /*
60 * set the handle size to zero so we copy only
61 * non variable part of the file_handle
62 */
63 handle_bytes = 0;
64 retval = -EOVERFLOW;
65 } else
66 retval = 0;
67 /* copy the mount id */
68 if (copy_to_user(mnt_id, &path->mnt->mnt_id, sizeof(*mnt_id)) ||
69 copy_to_user(ufh, handle,
70 sizeof(struct file_handle) + handle_bytes))
71 retval = -EFAULT;
72 kfree(handle);
73 return retval;
74}
75
76/**
77 * sys_name_to_handle_at: convert name to handle
78 * @dfd: directory relative to which name is interpreted if not absolute
79 * @name: name that should be converted to handle.
80 * @handle: resulting file handle
81 * @mnt_id: mount id of the file system containing the file
82 * @flag: flag value to indicate whether to follow symlink or not
83 *
84 * @handle->handle_size indicate the space available to store the
85 * variable part of the file handle in bytes. If there is not
86 * enough space, the field is updated to return the minimum
87 * value required.
88 */
89SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
90 struct file_handle __user *, handle, int __user *, mnt_id,
91 int, flag)
92{
93 struct path path;
94 int lookup_flags;
95 int err;
96
97 if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
98 return -EINVAL;
99
100 lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
101 if (flag & AT_EMPTY_PATH)
102 lookup_flags |= LOOKUP_EMPTY;
103 err = user_path_at(dfd, name, lookup_flags, &path);
104 if (!err) {
105 err = do_sys_name_to_handle(&path, handle, mnt_id);
106 path_put(&path);
107 }
108 return err;
109}
110
111static struct vfsmount *get_vfsmount_from_fd(int fd)
112{
113 struct path path;
114
115 if (fd == AT_FDCWD) {
116 struct fs_struct *fs = current->fs;
117 spin_lock(&fs->lock);
118 path = fs->pwd;
119 mntget(path.mnt);
120 spin_unlock(&fs->lock);
121 } else {
122 int fput_needed;
123 struct file *file = fget_light(fd, &fput_needed);
124 if (!file)
125 return ERR_PTR(-EBADF);
126 path = file->f_path;
127 mntget(path.mnt);
128 fput_light(file, fput_needed);
129 }
130 return path.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 if (copy_from_user(handle, ufh,
199 sizeof(struct file_handle) +
200 f_handle.handle_bytes)) {
201 retval = -EFAULT;
202 goto out_handle;
203 }
204
205 retval = do_handle_to_path(mountdirfd, handle, path);
206
207out_handle:
208 kfree(handle);
209out_err:
210 return retval;
211}
212
213long do_handle_open(int mountdirfd,
214 struct file_handle __user *ufh, int open_flag)
215{
216 long retval = 0;
217 struct path path;
218 struct file *file;
219 int fd;
220
221 retval = handle_to_path(mountdirfd, ufh, &path);
222 if (retval)
223 return retval;
224
225 fd = get_unused_fd_flags(open_flag);
226 if (fd < 0) {
227 path_put(&path);
228 return fd;
229 }
230 file = file_open_root(path.dentry, path.mnt, "", open_flag);
231 if (IS_ERR(file)) {
232 put_unused_fd(fd);
233 retval = PTR_ERR(file);
234 } else {
235 retval = fd;
236 fsnotify_open(file);
237 fd_install(fd, file);
238 }
239 path_put(&path);
240 return retval;
241}
242
243/**
244 * sys_open_by_handle_at: Open the file handle
245 * @mountdirfd: directory file descriptor
246 * @handle: file handle to be opened
247 * @flag: open flags.
248 *
249 * @mountdirfd indicate the directory file descriptor
250 * of the mount point. file handle is decoded relative
251 * to the vfsmount pointed by the @mountdirfd. @flags
252 * value is same as the open(2) flags.
253 */
254SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
255 struct file_handle __user *, handle,
256 int, flags)
257{
258 long ret;
259
260 if (force_o_largefile())
261 flags |= O_LARGEFILE;
262
263 ret = do_handle_open(mountdirfd, handle, flags);
264 return ret;
265}
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-15 09:35:47 -0500