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1// SPDX-License-Identifier: MIT
2/*
3 * VirtualBox Guest Shared Folders support: Regular file inode and file ops.
4 *
5 * Copyright (C) 2006-2018 Oracle Corporation
6 */
7
8#include <linux/mm.h>
9#include <linux/page-flags.h>
10#include <linux/pagemap.h>
11#include <linux/highmem.h>
12#include <linux/sizes.h>
13#include "vfsmod.h"
14
15struct vboxsf_handle {
16 u64 handle;
17 u32 root;
18 u32 access_flags;
19 struct kref refcount;
20 struct list_head head;
21};
22
23struct vboxsf_handle *vboxsf_create_sf_handle(struct inode *inode,
24 u64 handle, u32 access_flags)
25{
26 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
27 struct vboxsf_handle *sf_handle;
28
29 sf_handle = kmalloc(sizeof(*sf_handle), GFP_KERNEL);
30 if (!sf_handle)
31 return ERR_PTR(-ENOMEM);
32
33 /* the host may have given us different attr then requested */
34 sf_i->force_restat = 1;
35
36 /* init our handle struct and add it to the inode's handles list */
37 sf_handle->handle = handle;
38 sf_handle->root = VBOXSF_SBI(inode->i_sb)->root;
39 sf_handle->access_flags = access_flags;
40 kref_init(&sf_handle->refcount);
41
42 mutex_lock(&sf_i->handle_list_mutex);
43 list_add(&sf_handle->head, &sf_i->handle_list);
44 mutex_unlock(&sf_i->handle_list_mutex);
45
46 return sf_handle;
47}
48
49static int vboxsf_file_open(struct inode *inode, struct file *file)
50{
51 struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
52 struct shfl_createparms params = {};
53 struct vboxsf_handle *sf_handle;
54 u32 access_flags = 0;
55 int err;
56
57 /*
58 * We check the value of params.handle afterwards to find out if
59 * the call succeeded or failed, as the API does not seem to cleanly
60 * distinguish error and informational messages.
61 *
62 * Furthermore, we must set params.handle to SHFL_HANDLE_NIL to
63 * make the shared folders host service use our mode parameter.
64 */
65 params.handle = SHFL_HANDLE_NIL;
66 if (file->f_flags & O_CREAT) {
67 params.create_flags |= SHFL_CF_ACT_CREATE_IF_NEW;
68 /*
69 * We ignore O_EXCL, as the Linux kernel seems to call create
70 * beforehand itself, so O_EXCL should always fail.
71 */
72 if (file->f_flags & O_TRUNC)
73 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
74 else
75 params.create_flags |= SHFL_CF_ACT_OPEN_IF_EXISTS;
76 } else {
77 params.create_flags |= SHFL_CF_ACT_FAIL_IF_NEW;
78 if (file->f_flags & O_TRUNC)
79 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
80 }
81
82 switch (file->f_flags & O_ACCMODE) {
83 case O_RDONLY:
84 access_flags |= SHFL_CF_ACCESS_READ;
85 break;
86
87 case O_WRONLY:
88 access_flags |= SHFL_CF_ACCESS_WRITE;
89 break;
90
91 case O_RDWR:
92 access_flags |= SHFL_CF_ACCESS_READWRITE;
93 break;
94
95 default:
96 WARN_ON(1);
97 }
98
99 if (file->f_flags & O_APPEND)
100 access_flags |= SHFL_CF_ACCESS_APPEND;
101
102 params.create_flags |= access_flags;
103 params.info.attr.mode = inode->i_mode;
104
105 err = vboxsf_create_at_dentry(file_dentry(file), ¶ms);
106 if (err == 0 && params.handle == SHFL_HANDLE_NIL)
107 err = (params.result == SHFL_FILE_EXISTS) ? -EEXIST : -ENOENT;
108 if (err)
109 return err;
110
111 sf_handle = vboxsf_create_sf_handle(inode, params.handle, access_flags);
112 if (IS_ERR(sf_handle)) {
113 vboxsf_close(sbi->root, params.handle);
114 return PTR_ERR(sf_handle);
115 }
116
117 file->private_data = sf_handle;
118 return 0;
119}
120
121static void vboxsf_handle_release(struct kref *refcount)
122{
123 struct vboxsf_handle *sf_handle =
124 container_of(refcount, struct vboxsf_handle, refcount);
125
126 vboxsf_close(sf_handle->root, sf_handle->handle);
127 kfree(sf_handle);
128}
129
130void vboxsf_release_sf_handle(struct inode *inode, struct vboxsf_handle *sf_handle)
131{
132 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
133
134 mutex_lock(&sf_i->handle_list_mutex);
135 list_del(&sf_handle->head);
136 mutex_unlock(&sf_i->handle_list_mutex);
137
138 kref_put(&sf_handle->refcount, vboxsf_handle_release);
139}
140
141static int vboxsf_file_release(struct inode *inode, struct file *file)
142{
143 /*
144 * When a file is closed on our (the guest) side, we want any subsequent
145 * accesses done on the host side to see all changes done from our side.
146 */
147 filemap_write_and_wait(inode->i_mapping);
148
149 vboxsf_release_sf_handle(inode, file->private_data);
150 return 0;
151}
152
153/*
154 * Write back dirty pages now, because there may not be any suitable
155 * open files later
156 */
157static void vboxsf_vma_close(struct vm_area_struct *vma)
158{
159 filemap_write_and_wait(vma->vm_file->f_mapping);
160}
161
162static const struct vm_operations_struct vboxsf_file_vm_ops = {
163 .close = vboxsf_vma_close,
164 .fault = filemap_fault,
165 .map_pages = filemap_map_pages,
166};
167
168static int vboxsf_file_mmap(struct file *file, struct vm_area_struct *vma)
169{
170 int err;
171
172 err = generic_file_mmap(file, vma);
173 if (!err)
174 vma->vm_ops = &vboxsf_file_vm_ops;
175
176 return err;
177}
178
179/*
180 * Note that since we are accessing files on the host's filesystem, files
181 * may always be changed underneath us by the host!
182 *
183 * The vboxsf API between the guest and the host does not offer any functions
184 * to deal with this. There is no inode-generation to check for changes, no
185 * events / callback on changes and no way to lock files.
186 *
187 * To avoid returning stale data when a file gets *opened* on our (the guest)
188 * side, we do a "stat" on the host side, then compare the mtime with the
189 * last known mtime and invalidate the page-cache if they differ.
190 * This is done from vboxsf_inode_revalidate().
191 *
192 * When reads are done through the read_iter fop, it is possible to do
193 * further cache revalidation then, there are 3 options to deal with this:
194 *
195 * 1) Rely solely on the revalidation done at open time
196 * 2) Do another "stat" and compare mtime again. Unfortunately the vboxsf
197 * host API does not allow stat on handles, so we would need to use
198 * file->f_path.dentry and the stat will then fail if the file was unlinked
199 * or renamed (and there is no thing like NFS' silly-rename). So we get:
200 * 2a) "stat" and compare mtime, on stat failure invalidate the cache
201 * 2b) "stat" and compare mtime, on stat failure do nothing
202 * 3) Simply always call invalidate_inode_pages2_range on the range of the read
203 *
204 * Currently we are keeping things KISS and using option 1. this allows
205 * directly using generic_file_read_iter without wrapping it.
206 *
207 * This means that only data written on the host side before open() on
208 * the guest side is guaranteed to be seen by the guest. If necessary
209 * we may provide other read-cache strategies in the future and make this
210 * configurable through a mount option.
211 */
212const struct file_operations vboxsf_reg_fops = {
213 .llseek = generic_file_llseek,
214 .read_iter = generic_file_read_iter,
215 .write_iter = generic_file_write_iter,
216 .mmap = vboxsf_file_mmap,
217 .open = vboxsf_file_open,
218 .release = vboxsf_file_release,
219 .fsync = noop_fsync,
220 .splice_read = filemap_splice_read,
221};
222
223const struct inode_operations vboxsf_reg_iops = {
224 .getattr = vboxsf_getattr,
225 .setattr = vboxsf_setattr
226};
227
228static int vboxsf_read_folio(struct file *file, struct folio *folio)
229{
230 struct page *page = &folio->page;
231 struct vboxsf_handle *sf_handle = file->private_data;
232 loff_t off = page_offset(page);
233 u32 nread = PAGE_SIZE;
234 u8 *buf;
235 int err;
236
237 buf = kmap(page);
238
239 err = vboxsf_read(sf_handle->root, sf_handle->handle, off, &nread, buf);
240 if (err == 0) {
241 memset(&buf[nread], 0, PAGE_SIZE - nread);
242 flush_dcache_page(page);
243 SetPageUptodate(page);
244 } else {
245 SetPageError(page);
246 }
247
248 kunmap(page);
249 unlock_page(page);
250 return err;
251}
252
253static struct vboxsf_handle *vboxsf_get_write_handle(struct vboxsf_inode *sf_i)
254{
255 struct vboxsf_handle *h, *sf_handle = NULL;
256
257 mutex_lock(&sf_i->handle_list_mutex);
258 list_for_each_entry(h, &sf_i->handle_list, head) {
259 if (h->access_flags == SHFL_CF_ACCESS_WRITE ||
260 h->access_flags == SHFL_CF_ACCESS_READWRITE) {
261 kref_get(&h->refcount);
262 sf_handle = h;
263 break;
264 }
265 }
266 mutex_unlock(&sf_i->handle_list_mutex);
267
268 return sf_handle;
269}
270
271static int vboxsf_writepage(struct page *page, struct writeback_control *wbc)
272{
273 struct inode *inode = page->mapping->host;
274 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
275 struct vboxsf_handle *sf_handle;
276 loff_t off = page_offset(page);
277 loff_t size = i_size_read(inode);
278 u32 nwrite = PAGE_SIZE;
279 u8 *buf;
280 int err;
281
282 if (off + PAGE_SIZE > size)
283 nwrite = size & ~PAGE_MASK;
284
285 sf_handle = vboxsf_get_write_handle(sf_i);
286 if (!sf_handle)
287 return -EBADF;
288
289 buf = kmap(page);
290 err = vboxsf_write(sf_handle->root, sf_handle->handle,
291 off, &nwrite, buf);
292 kunmap(page);
293
294 kref_put(&sf_handle->refcount, vboxsf_handle_release);
295
296 if (err == 0) {
297 ClearPageError(page);
298 /* mtime changed */
299 sf_i->force_restat = 1;
300 } else {
301 ClearPageUptodate(page);
302 }
303
304 unlock_page(page);
305 return err;
306}
307
308static int vboxsf_write_end(struct file *file, struct address_space *mapping,
309 loff_t pos, unsigned int len, unsigned int copied,
310 struct page *page, void *fsdata)
311{
312 struct inode *inode = mapping->host;
313 struct vboxsf_handle *sf_handle = file->private_data;
314 unsigned int from = pos & ~PAGE_MASK;
315 u32 nwritten = len;
316 u8 *buf;
317 int err;
318
319 /* zero the stale part of the page if we did a short copy */
320 if (!PageUptodate(page) && copied < len)
321 zero_user(page, from + copied, len - copied);
322
323 buf = kmap(page);
324 err = vboxsf_write(sf_handle->root, sf_handle->handle,
325 pos, &nwritten, buf + from);
326 kunmap(page);
327
328 if (err) {
329 nwritten = 0;
330 goto out;
331 }
332
333 /* mtime changed */
334 VBOXSF_I(inode)->force_restat = 1;
335
336 if (!PageUptodate(page) && nwritten == PAGE_SIZE)
337 SetPageUptodate(page);
338
339 pos += nwritten;
340 if (pos > inode->i_size)
341 i_size_write(inode, pos);
342
343out:
344 unlock_page(page);
345 put_page(page);
346
347 return nwritten;
348}
349
350/*
351 * Note simple_write_begin does not read the page from disk on partial writes
352 * this is ok since vboxsf_write_end only writes the written parts of the
353 * page and it does not call SetPageUptodate for partial writes.
354 */
355const struct address_space_operations vboxsf_reg_aops = {
356 .read_folio = vboxsf_read_folio,
357 .writepage = vboxsf_writepage,
358 .dirty_folio = filemap_dirty_folio,
359 .write_begin = simple_write_begin,
360 .write_end = vboxsf_write_end,
361};
362
363static const char *vboxsf_get_link(struct dentry *dentry, struct inode *inode,
364 struct delayed_call *done)
365{
366 struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
367 struct shfl_string *path;
368 char *link;
369 int err;
370
371 if (!dentry)
372 return ERR_PTR(-ECHILD);
373
374 path = vboxsf_path_from_dentry(sbi, dentry);
375 if (IS_ERR(path))
376 return ERR_CAST(path);
377
378 link = kzalloc(PATH_MAX, GFP_KERNEL);
379 if (!link) {
380 __putname(path);
381 return ERR_PTR(-ENOMEM);
382 }
383
384 err = vboxsf_readlink(sbi->root, path, PATH_MAX, link);
385 __putname(path);
386 if (err) {
387 kfree(link);
388 return ERR_PTR(err);
389 }
390
391 set_delayed_call(done, kfree_link, link);
392 return link;
393}
394
395const struct inode_operations vboxsf_lnk_iops = {
396 .get_link = vboxsf_get_link
397};