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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> |
25 | #include <linux/slab.h> |
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 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, |
77 | (O_RDWR | O_LARGEFILE), current_cred()); |
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 | |
89 | int __init ecryptfs_init_kthread(void) |
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, |
136 | struct vfsmount *lower_mnt, |
137 | const struct cred *cred) |
138 | { |
139 | struct ecryptfs_open_req *req; |
140 | int flags = O_LARGEFILE; |
141 | int rc = 0; |
142 | |
143 | /* Corresponding dput() and mntput() are done when the |
144 | * lower file is fput() when all eCryptfs files for the inode are |
145 | * released. */ |
146 | dget(lower_dentry); |
147 | mntget(lower_mnt); |
148 | flags |= IS_RDONLY(lower_dentry->d_inode) ? O_RDONLY : O_RDWR; |
149 | (*lower_file) = dentry_open(lower_dentry, lower_mnt, flags, cred); |
150 | if (!IS_ERR(*lower_file)) |
151 | goto out; |
152 | if (flags & O_RDONLY) { |
153 | rc = PTR_ERR((*lower_file)); |
154 | goto out; |
155 | } |
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 | } |
189 | if (IS_ERR(*req->lower_file)) |
190 | rc = PTR_ERR(*req->lower_file); |
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 | } |
198 |
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