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746f1e55 MH |
1 | /** |
2 | * eCryptfs: Linux filesystem encryption layer | |
3 | * | |
4 | * Copyright (C) 2008 International Business Machines Corp. | |
5 | * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com> | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or | |
8 | * modify it under the terms of the GNU General Public License as | |
9 | * published by the Free Software Foundation; either version 2 of the | |
10 | * License, or (at your option) any later version. | |
11 | * | |
12 | * This program is distributed in the hope that it will be useful, but | |
13 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 | * General Public License for more details. | |
16 | * | |
17 | * You should have received a copy of the GNU General Public License | |
18 | * along with this program; if not, write to the Free Software | |
19 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA | |
20 | * 02111-1307, USA. | |
21 | */ | |
22 | ||
23 | #include <linux/kthread.h> | |
24 | #include <linux/freezer.h> | |
5a0e3ad6 | 25 | #include <linux/slab.h> |
746f1e55 MH |
26 | #include <linux/wait.h> |
27 | #include <linux/mount.h> | |
28 | #include "ecryptfs_kernel.h" | |
29 | ||
3b8b4871 AV |
30 | struct ecryptfs_open_req { |
31 | struct file **lower_file; | |
32 | struct dentry *lower_dentry; | |
33 | struct vfsmount *lower_mnt; | |
34 | struct completion done; | |
35 | struct list_head kthread_ctl_list; | |
36 | }; | |
746f1e55 MH |
37 | |
38 | static struct ecryptfs_kthread_ctl { | |
39 | #define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001 | |
40 | u32 flags; | |
41 | struct mutex mux; | |
42 | struct list_head req_list; | |
43 | wait_queue_head_t wait; | |
44 | } ecryptfs_kthread_ctl; | |
45 | ||
46 | static struct task_struct *ecryptfs_kthread; | |
47 | ||
48 | /** | |
49 | * ecryptfs_threadfn | |
50 | * @ignored: ignored | |
51 | * | |
52 | * The eCryptfs kernel thread that has the responsibility of getting | |
332ab16f | 53 | * the lower file with RW permissions. |
746f1e55 MH |
54 | * |
55 | * Returns zero on success; non-zero otherwise | |
56 | */ | |
57 | static int ecryptfs_threadfn(void *ignored) | |
58 | { | |
59 | set_freezable(); | |
60 | while (1) { | |
61 | struct ecryptfs_open_req *req; | |
62 | ||
63 | wait_event_freezable( | |
64 | ecryptfs_kthread_ctl.wait, | |
65 | (!list_empty(&ecryptfs_kthread_ctl.req_list) | |
66 | || kthread_should_stop())); | |
67 | mutex_lock(&ecryptfs_kthread_ctl.mux); | |
68 | if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) { | |
69 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
70 | goto out; | |
71 | } | |
72 | while (!list_empty(&ecryptfs_kthread_ctl.req_list)) { | |
73 | req = list_first_entry(&ecryptfs_kthread_ctl.req_list, | |
74 | struct ecryptfs_open_req, | |
75 | kthread_ctl_list); | |
746f1e55 | 76 | list_del(&req->kthread_ctl_list); |
3b8b4871 AV |
77 | dget(req->lower_dentry); |
78 | mntget(req->lower_mnt); | |
79 | (*req->lower_file) = dentry_open( | |
80 | req->lower_dentry, req->lower_mnt, | |
81 | (O_RDWR | O_LARGEFILE), current_cred()); | |
82 | complete(&req->done); | |
746f1e55 MH |
83 | } |
84 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
85 | } | |
86 | out: | |
87 | return 0; | |
88 | } | |
89 | ||
7371a382 | 90 | int __init ecryptfs_init_kthread(void) |
746f1e55 MH |
91 | { |
92 | int rc = 0; | |
93 | ||
94 | mutex_init(&ecryptfs_kthread_ctl.mux); | |
95 | init_waitqueue_head(&ecryptfs_kthread_ctl.wait); | |
96 | INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list); | |
97 | ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL, | |
98 | "ecryptfs-kthread"); | |
99 | if (IS_ERR(ecryptfs_kthread)) { | |
100 | rc = PTR_ERR(ecryptfs_kthread); | |
101 | printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]" | |
102 | "\n", __func__, rc); | |
103 | } | |
104 | return rc; | |
105 | } | |
106 | ||
107 | void ecryptfs_destroy_kthread(void) | |
108 | { | |
109 | struct ecryptfs_open_req *req; | |
110 | ||
111 | mutex_lock(&ecryptfs_kthread_ctl.mux); | |
112 | ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE; | |
113 | list_for_each_entry(req, &ecryptfs_kthread_ctl.req_list, | |
114 | kthread_ctl_list) { | |
3b8b4871 AV |
115 | list_del(&req->kthread_ctl_list); |
116 | *req->lower_file = ERR_PTR(-EIO); | |
117 | complete(&req->done); | |
746f1e55 MH |
118 | } |
119 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
120 | kthread_stop(ecryptfs_kthread); | |
121 | wake_up(&ecryptfs_kthread_ctl.wait); | |
122 | } | |
123 | ||
124 | /** | |
125 | * ecryptfs_privileged_open | |
126 | * @lower_file: Result of dentry_open by root on lower dentry | |
127 | * @lower_dentry: Lower dentry for file to open | |
128 | * @lower_mnt: Lower vfsmount for file to open | |
129 | * | |
130 | * This function gets a r/w file opened againt the lower dentry. | |
131 | * | |
132 | * Returns zero on success; non-zero otherwise | |
133 | */ | |
134 | int ecryptfs_privileged_open(struct file **lower_file, | |
135 | struct dentry *lower_dentry, | |
745ca247 DH |
136 | struct vfsmount *lower_mnt, |
137 | const struct cred *cred) | |
746f1e55 | 138 | { |
3b8b4871 | 139 | struct ecryptfs_open_req req; |
ac22ba23 | 140 | int flags = O_LARGEFILE; |
746f1e55 MH |
141 | int rc = 0; |
142 | ||
143 | /* Corresponding dput() and mntput() are done when the | |
332ab16f TH |
144 | * lower file is fput() when all eCryptfs files for the inode are |
145 | * released. */ | |
746f1e55 MH |
146 | dget(lower_dentry); |
147 | mntget(lower_mnt); | |
ac22ba23 TH |
148 | flags |= IS_RDONLY(lower_dentry->d_inode) ? O_RDONLY : O_RDWR; |
149 | (*lower_file) = dentry_open(lower_dentry, lower_mnt, flags, cred); | |
746f1e55 MH |
150 | if (!IS_ERR(*lower_file)) |
151 | goto out; | |
9fe79d76 | 152 | if ((flags & O_ACCMODE) == O_RDONLY) { |
ac22ba23 TH |
153 | rc = PTR_ERR((*lower_file)); |
154 | goto out; | |
155 | } | |
3b8b4871 AV |
156 | init_completion(&req.done); |
157 | req.lower_file = lower_file; | |
158 | req.lower_dentry = lower_dentry; | |
159 | req.lower_mnt = lower_mnt; | |
746f1e55 MH |
160 | mutex_lock(&ecryptfs_kthread_ctl.mux); |
161 | if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) { | |
162 | rc = -EIO; | |
163 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
164 | printk(KERN_ERR "%s: We are in the middle of shutting down; " | |
165 | "aborting privileged request to open lower file\n", | |
166 | __func__); | |
3b8b4871 | 167 | goto out; |
746f1e55 | 168 | } |
3b8b4871 | 169 | list_add_tail(&req.kthread_ctl_list, &ecryptfs_kthread_ctl.req_list); |
746f1e55 MH |
170 | mutex_unlock(&ecryptfs_kthread_ctl.mux); |
171 | wake_up(&ecryptfs_kthread_ctl.wait); | |
3b8b4871 AV |
172 | wait_for_completion(&req.done); |
173 | if (IS_ERR(*lower_file)) | |
174 | rc = PTR_ERR(*lower_file); | |
746f1e55 MH |
175 | out: |
176 | return rc; | |
177 | } |