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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 | ||
30 | struct kmem_cache *ecryptfs_open_req_cache; | |
31 | ||
32 | static struct ecryptfs_kthread_ctl { | |
33 | #define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001 | |
34 | u32 flags; | |
35 | struct mutex mux; | |
36 | struct list_head req_list; | |
37 | wait_queue_head_t wait; | |
38 | } ecryptfs_kthread_ctl; | |
39 | ||
40 | static struct task_struct *ecryptfs_kthread; | |
41 | ||
42 | /** | |
43 | * ecryptfs_threadfn | |
44 | * @ignored: ignored | |
45 | * | |
46 | * The eCryptfs kernel thread that has the responsibility of getting | |
47 | * the lower persistent file with RW permissions. | |
48 | * | |
49 | * Returns zero on success; non-zero otherwise | |
50 | */ | |
51 | static int ecryptfs_threadfn(void *ignored) | |
52 | { | |
53 | set_freezable(); | |
54 | while (1) { | |
55 | struct ecryptfs_open_req *req; | |
56 | ||
57 | wait_event_freezable( | |
58 | ecryptfs_kthread_ctl.wait, | |
59 | (!list_empty(&ecryptfs_kthread_ctl.req_list) | |
60 | || kthread_should_stop())); | |
61 | mutex_lock(&ecryptfs_kthread_ctl.mux); | |
62 | if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) { | |
63 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
64 | goto out; | |
65 | } | |
66 | while (!list_empty(&ecryptfs_kthread_ctl.req_list)) { | |
67 | req = list_first_entry(&ecryptfs_kthread_ctl.req_list, | |
68 | struct ecryptfs_open_req, | |
69 | kthread_ctl_list); | |
70 | mutex_lock(&req->mux); | |
71 | list_del(&req->kthread_ctl_list); | |
72 | if (!(req->flags & ECRYPTFS_REQ_ZOMBIE)) { | |
73 | dget(req->lower_dentry); | |
74 | mntget(req->lower_mnt); | |
75 | (*req->lower_file) = dentry_open( | |
76 | req->lower_dentry, req->lower_mnt, | |
745ca247 | 77 | (O_RDWR | O_LARGEFILE), current_cred()); |
746f1e55 MH |
78 | req->flags |= ECRYPTFS_REQ_PROCESSED; |
79 | } | |
80 | wake_up(&req->wait); | |
81 | mutex_unlock(&req->mux); | |
82 | } | |
83 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
84 | } | |
85 | out: | |
86 | return 0; | |
87 | } | |
88 | ||
7371a382 | 89 | int __init ecryptfs_init_kthread(void) |
746f1e55 MH |
90 | { |
91 | int rc = 0; | |
92 | ||
93 | mutex_init(&ecryptfs_kthread_ctl.mux); | |
94 | init_waitqueue_head(&ecryptfs_kthread_ctl.wait); | |
95 | INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list); | |
96 | ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL, | |
97 | "ecryptfs-kthread"); | |
98 | if (IS_ERR(ecryptfs_kthread)) { | |
99 | rc = PTR_ERR(ecryptfs_kthread); | |
100 | printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]" | |
101 | "\n", __func__, rc); | |
102 | } | |
103 | return rc; | |
104 | } | |
105 | ||
106 | void ecryptfs_destroy_kthread(void) | |
107 | { | |
108 | struct ecryptfs_open_req *req; | |
109 | ||
110 | mutex_lock(&ecryptfs_kthread_ctl.mux); | |
111 | ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE; | |
112 | list_for_each_entry(req, &ecryptfs_kthread_ctl.req_list, | |
113 | kthread_ctl_list) { | |
114 | mutex_lock(&req->mux); | |
115 | req->flags |= ECRYPTFS_REQ_ZOMBIE; | |
116 | wake_up(&req->wait); | |
117 | mutex_unlock(&req->mux); | |
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 MH |
138 | { |
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 | |
144 | * persistent file is fput() when the eCryptfs inode is | |
145 | * destroyed. */ | |
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; | |
ac22ba23 TH |
152 | if (flags & O_RDONLY) { |
153 | rc = PTR_ERR((*lower_file)); | |
154 | goto out; | |
155 | } | |
746f1e55 MH |
156 | req = kmem_cache_alloc(ecryptfs_open_req_cache, GFP_KERNEL); |
157 | if (!req) { | |
158 | rc = -ENOMEM; | |
159 | goto out; | |
160 | } | |
161 | mutex_init(&req->mux); | |
162 | req->lower_file = lower_file; | |
163 | req->lower_dentry = lower_dentry; | |
164 | req->lower_mnt = lower_mnt; | |
165 | init_waitqueue_head(&req->wait); | |
166 | req->flags = 0; | |
167 | mutex_lock(&ecryptfs_kthread_ctl.mux); | |
168 | if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) { | |
169 | rc = -EIO; | |
170 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
171 | printk(KERN_ERR "%s: We are in the middle of shutting down; " | |
172 | "aborting privileged request to open lower file\n", | |
173 | __func__); | |
174 | goto out_free; | |
175 | } | |
176 | list_add_tail(&req->kthread_ctl_list, &ecryptfs_kthread_ctl.req_list); | |
177 | mutex_unlock(&ecryptfs_kthread_ctl.mux); | |
178 | wake_up(&ecryptfs_kthread_ctl.wait); | |
179 | wait_event(req->wait, (req->flags != 0)); | |
180 | mutex_lock(&req->mux); | |
181 | BUG_ON(req->flags == 0); | |
182 | if (req->flags & ECRYPTFS_REQ_DROPPED | |
183 | || req->flags & ECRYPTFS_REQ_ZOMBIE) { | |
184 | rc = -EIO; | |
185 | printk(KERN_WARNING "%s: Privileged open request dropped\n", | |
186 | __func__); | |
187 | goto out_unlock; | |
188 | } | |
ac22ba23 | 189 | if (IS_ERR(*req->lower_file)) |
746f1e55 | 190 | rc = PTR_ERR(*req->lower_file); |
746f1e55 MH |
191 | out_unlock: |
192 | mutex_unlock(&req->mux); | |
193 | out_free: | |
194 | kmem_cache_free(ecryptfs_open_req_cache, req); | |
195 | out: | |
196 | return rc; | |
197 | } |