1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* mountpoint management
3 *
4 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/kernel.h>
9 #include <linux/module.h>
10 #include <linux/init.h>
11 #include <linux/fs.h>
12 #include <linux/pagemap.h>
13 #include <linux/mount.h>
14 #include <linux/namei.h>
15 #include <linux/gfp.h>
16 #include <linux/fs_context.h>
17 #include "internal.h"
18
19
20 static struct dentry *afs_mntpt_lookup(struct inode *dir,
21 struct dentry *dentry,
22 unsigned int flags);
23 static int afs_mntpt_open(struct inode *inode, struct file *file);
24 static void afs_mntpt_expiry_timed_out(struct work_struct *work);
25
26 const struct file_operations afs_mntpt_file_operations = {
27 .open = afs_mntpt_open,
28 .llseek = noop_llseek,
29 };
30
31 const struct inode_operations afs_mntpt_inode_operations = {
32 .lookup = afs_mntpt_lookup,
33 .readlink = page_readlink,
34 .getattr = afs_getattr,
35 };
36
37 const struct inode_operations afs_autocell_inode_operations = {
38 .getattr = afs_getattr,
39 };
40
41 static LIST_HEAD(afs_vfsmounts);
42 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
43
44 static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
45
46 static const char afs_root_volume[] = "root.cell";
47
48 /*
49 * no valid lookup procedure on this sort of dir
50 */
51 static struct dentry *afs_mntpt_lookup(struct inode *dir,
52 struct dentry *dentry,
53 unsigned int flags)
54 {
55 _enter("%p,%p{%pd2}", dir, dentry, dentry);
56 return ERR_PTR(-EREMOTE);
57 }
58
59 /*
60 * no valid open procedure on this sort of dir
61 */
62 static int afs_mntpt_open(struct inode *inode, struct file *file)
63 {
64 _enter("%p,%p{%pD2}", inode, file, file);
65 return -EREMOTE;
66 }
67
68 /*
69 * Set the parameters for the proposed superblock.
70 */
71 static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
72 {
73 struct afs_fs_context *ctx = fc->fs_private;
74 struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
75 struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
76 struct afs_cell *cell;
77 const char *p;
78 int ret;
79
80 if (fc->net_ns != src_as->net_ns) {
81 put_net(fc->net_ns);
82 fc->net_ns = get_net(src_as->net_ns);
83 }
84
85 if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
86 ctx->type = AFSVL_RWVOL;
87 ctx->force = true;
88 }
89 if (ctx->cell) {
90 afs_unuse_cell(ctx->net, ctx->cell, afs_cell_trace_unuse_mntpt);
91 ctx->cell = NULL;
92 }
93 if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
94 /* if the directory is a pseudo directory, use the d_name */
95 unsigned size = mntpt->d_name.len;
96
97 if (size < 2)
98 return -ENOENT;
99
100 p = mntpt->d_name.name;
101 if (mntpt->d_name.name[0] == '.') {
102 size--;
103 p++;
104 ctx->type = AFSVL_RWVOL;
105 ctx->force = true;
106 }
107 if (size > AFS_MAXCELLNAME)
108 return -ENAMETOOLONG;
109
110 cell = afs_lookup_cell(ctx->net, p, size, NULL, false);
111 if (IS_ERR(cell)) {
112 pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
113 return PTR_ERR(cell);
114 }
115 ctx->cell = cell;
116
117 ctx->volname = afs_root_volume;
118 ctx->volnamesz = sizeof(afs_root_volume) - 1;
119 } else {
120 /* read the contents of the AFS special symlink */
121 struct page *page;
122 loff_t size = i_size_read(d_inode(mntpt));
123 char *buf;
124
125 if (src_as->cell)
126 ctx->cell = afs_use_cell(src_as->cell, afs_cell_trace_use_mntpt);
127
128 if (size < 2 || size > PAGE_SIZE - 1)
129 return -EINVAL;
130
131 page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
132 if (IS_ERR(page))
133 return PTR_ERR(page);
134
135 buf = kmap(page);
136 ret = -EINVAL;
137 if (buf[size - 1] == '.')
138 ret = vfs_parse_fs_string(fc, "source", buf, size - 1);
139 kunmap(page);
140 put_page(page);
141 if (ret < 0)
142 return ret;
143
144 /* Don't cross a backup volume mountpoint from a backup volume */
145 if (src_as->volume && src_as->volume->type == AFSVL_BACKVOL &&
146 ctx->type == AFSVL_BACKVOL)
147 return -ENODEV;
148 }
149
150 return 0;
151 }
152
153 /*
154 * create a vfsmount to be automounted
155 */
156 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
157 {
158 struct fs_context *fc;
159 struct vfsmount *mnt;
160 int ret;
161
162 BUG_ON(!d_inode(mntpt));
163
164 fc = fs_context_for_submount(&afs_fs_type, mntpt);
165 if (IS_ERR(fc))
166 return ERR_CAST(fc);
167
168 ret = afs_mntpt_set_params(fc, mntpt);
169 if (!ret)
170 mnt = fc_mount(fc);
171 else
172 mnt = ERR_PTR(ret);
173
174 put_fs_context(fc);
175 return mnt;
176 }
177
178 /*
179 * handle an automount point
180 */
181 struct vfsmount *afs_d_automount(struct path *path)
182 {
183 struct vfsmount *newmnt;
184
185 _enter("{%pd}", path->dentry);
186
187 newmnt = afs_mntpt_do_automount(path->dentry);
188 if (IS_ERR(newmnt))
189 return newmnt;
190
191 mntget(newmnt); /* prevent immediate expiration */
192 mnt_set_expiry(newmnt, &afs_vfsmounts);
193 queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
194 afs_mntpt_expiry_timeout * HZ);
195 _leave(" = %p", newmnt);
196 return newmnt;
197 }
198
199 /*
200 * handle mountpoint expiry timer going off
201 */
202 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
203 {
204 _enter("");
205
206 if (!list_empty(&afs_vfsmounts)) {
207 mark_mounts_for_expiry(&afs_vfsmounts);
208 queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
209 afs_mntpt_expiry_timeout * HZ);
210 }
211
212 _leave("");
213 }
214
215 /*
216 * kill the AFS mountpoint timer if it's still running
217 */
218 void afs_mntpt_kill_timer(void)
219 {
220 _enter("");
221
222 ASSERT(list_empty(&afs_vfsmounts));
223 cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
224 }
225
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