blob: 5559168d5637310d2712eab97af1117a786cfba1 [file] [log] [blame]
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +05301#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>
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +05308#include <linux/fs_struct.h>
9#include <linux/fsnotify.h>
Jeff Mahoneyed5afea2011-04-14 15:22:16 -070010#include <linux/personality.h>
Linus Torvalds7c0f6ba2016-12-24 11:46:01 -080011#include <linux/uaccess.h>
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +053012#include "internal.h"
Al Viro15169fe2011-11-25 00:50:41 -050013#include "mount.h"
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +053014
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 /*
Adam Buchbinder48fc7f72012-09-19 21:48:00 -040025 * We need to make sure whether the file system
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +053026 * support decoding of the file handle
27 */
Al Virod8c95842011-12-07 18:16:57 -050028 if (!path->dentry->d_sb->s_export_op ||
29 !path->dentry->d_sb->s_export_op->fh_to_dentry)
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +053030 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
Adam Buchbinder48fc7f72012-09-19 21:48:00 -040043 /* convert handle size to multiple of sizeof(u32) */
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +053044 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) ||
Namjae Jeon216b6cb2012-08-29 10:10:10 -040055 (retval == FILEID_INVALID) || (retval == -ENOSPC)) {
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +053056 /* 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 */
Al Viro15169fe2011-11-25 00:50:41 -050070 if (copy_to_user(mnt_id, &real_mount(path->mnt)->mnt_id,
71 sizeof(*mnt_id)) ||
Aneesh Kumar K.V990d6c22011-01-29 18:43:26 +053072 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}
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530113
114static struct vfsmount *get_vfsmount_from_fd(int fd)
115{
Al Viro2903ff02012-08-28 12:52:22 -0400116 struct vfsmount *mnt;
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530117
118 if (fd == AT_FDCWD) {
119 struct fs_struct *fs = current->fs;
120 spin_lock(&fs->lock);
Al Viro2903ff02012-08-28 12:52:22 -0400121 mnt = mntget(fs->pwd.mnt);
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530122 spin_unlock(&fs->lock);
123 } else {
Al Viro2903ff02012-08-28 12:52:22 -0400124 struct fd f = fdget(fd);
125 if (!f.file)
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530126 return ERR_PTR(-EBADF);
Al Viro2903ff02012-08-28 12:52:22 -0400127 mnt = mntget(f.file->f_path.mnt);
128 fdput(f);
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530129 }
Al Viro2903ff02012-08-28 12:52:22 -0400130 return mnt;
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530131}
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 */
Sasha Levin161f873b2015-01-28 15:30:43 -0500198 *handle = f_handle;
199 if (copy_from_user(&handle->f_handle,
200 &ufh->f_handle,
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530201 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 }
Jann Horn378c6522016-03-22 14:25:36 -0700231 file = file_open_root(path.dentry, path.mnt, "", open_flag, 0);
Aneesh Kumar K.Vbecfd1f2011-01-29 18:43:26 +0530232 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}