1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * eCryptfs: Linux filesystem encryption layer
4 *
5 * Copyright (C) 2008 International Business Machines Corp.
6 * Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
7 */
8
9 #include <linux/kthread.h>
10 #include <linux/freezer.h>
11 #include <linux/slab.h>
12 #include <linux/wait.h>
13 #include <linux/mount.h>
14 #include "ecryptfs_kernel.h"
15
16 struct ecryptfs_open_req {
17 struct file **lower_file;
18 struct path path;
19 struct completion done;
20 struct list_head kthread_ctl_list;
21 };
22
23 static struct ecryptfs_kthread_ctl {
24 #define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001
25 u32 flags;
26 struct mutex mux;
27 struct list_head req_list;
28 wait_queue_head_t wait;
29 } ecryptfs_kthread_ctl;
30
31 static struct task_struct *ecryptfs_kthread;
32
33 /**
34 * ecryptfs_threadfn
35 * @ignored: ignored
36 *
37 * The eCryptfs kernel thread that has the responsibility of getting
38 * the lower file with RW permissions.
39 *
40 * Returns zero on success; non-zero otherwise
41 */
ecryptfs_threadfn(void * ignored)42 static int ecryptfs_threadfn(void *ignored)
43 {
44 set_freezable();
45 while (1) {
46 struct ecryptfs_open_req *req;
47
48 wait_event_freezable(
49 ecryptfs_kthread_ctl.wait,
50 (!list_empty(&ecryptfs_kthread_ctl.req_list)
51 || kthread_should_stop()));
52 mutex_lock(&ecryptfs_kthread_ctl.mux);
53 if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
54 mutex_unlock(&ecryptfs_kthread_ctl.mux);
55 goto out;
56 }
57 while (!list_empty(&ecryptfs_kthread_ctl.req_list)) {
58 req = list_first_entry(&ecryptfs_kthread_ctl.req_list,
59 struct ecryptfs_open_req,
60 kthread_ctl_list);
61 list_del(&req->kthread_ctl_list);
62 *req->lower_file = dentry_open(&req->path,
63 (O_RDWR | O_LARGEFILE), current_cred());
64 complete(&req->done);
65 }
66 mutex_unlock(&ecryptfs_kthread_ctl.mux);
67 }
68 out:
69 return 0;
70 }
71
ecryptfs_init_kthread(void)72 int __init ecryptfs_init_kthread(void)
73 {
74 int rc = 0;
75
76 mutex_init(&ecryptfs_kthread_ctl.mux);
77 init_waitqueue_head(&ecryptfs_kthread_ctl.wait);
78 INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list);
79 ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL,
80 "ecryptfs-kthread");
81 if (IS_ERR(ecryptfs_kthread)) {
82 rc = PTR_ERR(ecryptfs_kthread);
83 printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]"
84 "\n", __func__, rc);
85 }
86 return rc;
87 }
88
ecryptfs_destroy_kthread(void)89 void ecryptfs_destroy_kthread(void)
90 {
91 struct ecryptfs_open_req *req, *tmp;
92
93 mutex_lock(&ecryptfs_kthread_ctl.mux);
94 ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE;
95 list_for_each_entry_safe(req, tmp, &ecryptfs_kthread_ctl.req_list,
96 kthread_ctl_list) {
97 list_del(&req->kthread_ctl_list);
98 *req->lower_file = ERR_PTR(-EIO);
99 complete(&req->done);
100 }
101 mutex_unlock(&ecryptfs_kthread_ctl.mux);
102 kthread_stop(ecryptfs_kthread);
103 wake_up(&ecryptfs_kthread_ctl.wait);
104 }
105
106 /**
107 * ecryptfs_privileged_open
108 * @lower_file: Result of dentry_open by root on lower dentry
109 * @lower_dentry: Lower dentry for file to open
110 * @lower_mnt: Lower vfsmount for file to open
111 * @cred: credential to use for this call
112 *
113 * This function gets a r/w file opened against the lower dentry.
114 *
115 * Returns zero on success; non-zero otherwise
116 */
ecryptfs_privileged_open(struct file ** lower_file,struct dentry * lower_dentry,struct vfsmount * lower_mnt,const struct cred * cred)117 int ecryptfs_privileged_open(struct file **lower_file,
118 struct dentry *lower_dentry,
119 struct vfsmount *lower_mnt,
120 const struct cred *cred)
121 {
122 struct ecryptfs_open_req req;
123 int flags = O_LARGEFILE;
124 int rc = 0;
125
126 init_completion(&req.done);
127 req.lower_file = lower_file;
128 req.path.dentry = lower_dentry;
129 req.path.mnt = lower_mnt;
130
131 /* Corresponding dput() and mntput() are done when the
132 * lower file is fput() when all eCryptfs files for the inode are
133 * released. */
134 flags |= IS_RDONLY(d_inode(lower_dentry)) ? O_RDONLY : O_RDWR;
135 (*lower_file) = dentry_open(&req.path, flags, cred);
136 if (!IS_ERR(*lower_file))
137 goto out;
138 if ((flags & O_ACCMODE) == O_RDONLY) {
139 rc = PTR_ERR((*lower_file));
140 goto out;
141 }
142 mutex_lock(&ecryptfs_kthread_ctl.mux);
143 if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
144 rc = -EIO;
145 mutex_unlock(&ecryptfs_kthread_ctl.mux);
146 printk(KERN_ERR "%s: We are in the middle of shutting down; "
147 "aborting privileged request to open lower file\n",
148 __func__);
149 goto out;
150 }
151 list_add_tail(&req.kthread_ctl_list, &ecryptfs_kthread_ctl.req_list);
152 mutex_unlock(&ecryptfs_kthread_ctl.mux);
153 wake_up(&ecryptfs_kthread_ctl.wait);
154 wait_for_completion(&req.done);
155 if (IS_ERR(*lower_file))
156 rc = PTR_ERR(*lower_file);
157 out:
158 return rc;
159 }
160