5 files changed, 251 insertions, 22 deletions

diff --git a/fs/ecryptfs/Makefile b/fs/ecryptfs/Makefile
index 1e34a7fd4884..b4755a85996e 100644
--- a/fs/ecryptfs/Makefile
+++ b/fs/ecryptfs/Makefile
@@ -4,4 +4,4 @@
 
 obj-$(CONFIG_ECRYPT_FS) += ecryptfs.o
 
-ecryptfs-objs := dentry.o file.o inode.o main.o super.o mmap.o read_write.o crypto.o keystore.o messaging.o netlink.o miscdev.o debug.o
+ecryptfs-objs := dentry.o file.o inode.o main.o super.o mmap.o read_write.o crypto.o keystore.o messaging.o netlink.o miscdev.o kthread.o debug.o
diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index c15c25745e05..b4a0cccfdd7c 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -559,6 +559,20 @@ extern struct kmem_cache *ecryptfs_key_record_cache;
 extern struct kmem_cache *ecryptfs_key_sig_cache;
 extern struct kmem_cache *ecryptfs_global_auth_tok_cache;
 extern struct kmem_cache *ecryptfs_key_tfm_cache;
+extern struct kmem_cache *ecryptfs_open_req_cache;
+
+struct ecryptfs_open_req {
+#define ECRYPTFS_REQ_PROCESSED 0x00000001
+#define ECRYPTFS_REQ_DROPPED   0x00000002
+#define ECRYPTFS_REQ_ZOMBIE    0x00000004
+        u32 flags;
+        struct file **lower_file;
+        struct dentry *lower_dentry;
+        struct vfsmount *lower_mnt;
+        wait_queue_head_t wait;
+        struct mutex mux;
+        struct list_head kthread_ctl_list;
+};
 
 int ecryptfs_interpose(struct dentry *hidden_dentry,
                        struct dentry *this_dentry, struct super_block *sb,
@@ -690,5 +704,10 @@ void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx);
 int
 ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, uid_t euid,
                       struct user_namespace *user_ns, struct pid *pid);
+int ecryptfs_init_kthread(void);
+void ecryptfs_destroy_kthread(void);
+int ecryptfs_privileged_open(struct file **lower_file,
+                             struct dentry *lower_dentry,
+                             struct vfsmount *lower_mnt);
 
 #endif /* #ifndef ECRYPTFS_KERNEL_H */
diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index 24749bf0668f..f0be29051528 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -192,6 +192,13 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
                                       | ECRYPTFS_ENCRYPTED);
         }
         mutex_unlock(&crypt_stat->cs_mutex);
+        if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_RDONLY)
+            && !(file->f_flags & O_RDONLY)) {
+                rc = -EPERM;
+                printk(KERN_WARNING "%s: Lower persistent file is RO; eCryptfs "
+                       "file must hence be opened RO\n", __func__);
+                goto out;
+        }
         ecryptfs_set_file_lower(
                 file, ecryptfs_inode_to_private(inode)->lower_file);
         if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {
diff --git a/fs/ecryptfs/kthread.c b/fs/ecryptfs/kthread.c
new file mode 100644
index 000000000000..c440c6b58b2d
--- /dev/null
+++ b/fs/ecryptfs/kthread.c
@@ -0,0 +1,203 @@
+/**
+ * eCryptfs: Linux filesystem encryption layer
+ *
+ * Copyright (C) 2008 International Business Machines Corp.
+ *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/wait.h>
+#include <linux/mount.h>
+#include "ecryptfs_kernel.h"
+
+struct kmem_cache *ecryptfs_open_req_cache;
+
+static struct ecryptfs_kthread_ctl {
+#define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001
+        u32 flags;
+        struct mutex mux;
+        struct list_head req_list;
+        wait_queue_head_t wait;
+} ecryptfs_kthread_ctl;
+
+static struct task_struct *ecryptfs_kthread;
+
+/**
+ * ecryptfs_threadfn
+ * @ignored: ignored
+ *
+ * The eCryptfs kernel thread that has the responsibility of getting
+ * the lower persistent file with RW permissions.
+ *
+ * Returns zero on success; non-zero otherwise
+ */
+static int ecryptfs_threadfn(void *ignored)
+{
+        set_freezable();
+        while (1)  {
+                struct ecryptfs_open_req *req;
+
+                wait_event_freezable(
+                        ecryptfs_kthread_ctl.wait,
+                        (!list_empty(&ecryptfs_kthread_ctl.req_list)
+                         || kthread_should_stop()));
+                mutex_lock(&ecryptfs_kthread_ctl.mux);
+                if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
+                        mutex_unlock(&ecryptfs_kthread_ctl.mux);
+                        goto out;
+                }
+                while (!list_empty(&ecryptfs_kthread_ctl.req_list)) {
+                        req = list_first_entry(&ecryptfs_kthread_ctl.req_list,
+                                               struct ecryptfs_open_req,
+                                               kthread_ctl_list);
+                        mutex_lock(&req->mux);
+                        list_del(&req->kthread_ctl_list);
+                        if (!(req->flags & ECRYPTFS_REQ_ZOMBIE)) {
+                                dget(req->lower_dentry);
+                                mntget(req->lower_mnt);
+                                (*req->lower_file) = dentry_open(
+                                        req->lower_dentry, req->lower_mnt,
+                                        (O_RDWR | O_LARGEFILE));
+                                req->flags |= ECRYPTFS_REQ_PROCESSED;
+                        }
+                        wake_up(&req->wait);
+                        mutex_unlock(&req->mux);
+                }
+                mutex_unlock(&ecryptfs_kthread_ctl.mux);
+        }
+out:
+        return 0;
+}
+
+int ecryptfs_init_kthread(void)
+{
+        int rc = 0;
+
+        mutex_init(&ecryptfs_kthread_ctl.mux);
+        init_waitqueue_head(&ecryptfs_kthread_ctl.wait);
+        INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list);
+        ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL,
+                                       "ecryptfs-kthread");
+        if (IS_ERR(ecryptfs_kthread)) {
+                rc = PTR_ERR(ecryptfs_kthread);
+                printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]"
+                       "\n", __func__, rc);
+        }
+        return rc;
+}
+
+void ecryptfs_destroy_kthread(void)
+{
+        struct ecryptfs_open_req *req;
+
+        mutex_lock(&ecryptfs_kthread_ctl.mux);
+        ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE;
+        list_for_each_entry(req, &ecryptfs_kthread_ctl.req_list,
+                            kthread_ctl_list) {
+                mutex_lock(&req->mux);
+                req->flags |= ECRYPTFS_REQ_ZOMBIE;
+                wake_up(&req->wait);
+                mutex_unlock(&req->mux);
+        }
+        mutex_unlock(&ecryptfs_kthread_ctl.mux);
+        kthread_stop(ecryptfs_kthread);
+        wake_up(&ecryptfs_kthread_ctl.wait);
+}
+
+/**
+ * ecryptfs_privileged_open
+ * @lower_file: Result of dentry_open by root on lower dentry
+ * @lower_dentry: Lower dentry for file to open
+ * @lower_mnt: Lower vfsmount for file to open
+ *
+ * This function gets a r/w file opened againt the lower dentry.
+ *
+ * Returns zero on success; non-zero otherwise
+ */
+int ecryptfs_privileged_open(struct file **lower_file,
+                             struct dentry *lower_dentry,
+                             struct vfsmount *lower_mnt)
+{
+        struct ecryptfs_open_req *req;
+        int rc = 0;
+
+        /* Corresponding dput() and mntput() are done when the
+         * persistent file is fput() when the eCryptfs inode is
+         * destroyed. */
+        dget(lower_dentry);
+        mntget(lower_mnt);
+        (*lower_file) = dentry_open(lower_dentry, lower_mnt,
+                                    (O_RDWR | O_LARGEFILE));
+        if (!IS_ERR(*lower_file))
+                goto out;
+        req = kmem_cache_alloc(ecryptfs_open_req_cache, GFP_KERNEL);
+        if (!req) {
+                rc = -ENOMEM;
+                goto out;
+        }
+        mutex_init(&req->mux);
+        req->lower_file = lower_file;
+        req->lower_dentry = lower_dentry;
+        req->lower_mnt = lower_mnt;
+        init_waitqueue_head(&req->wait);
+        req->flags = 0;
+        mutex_lock(&ecryptfs_kthread_ctl.mux);
+        if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
+                rc = -EIO;
+                mutex_unlock(&ecryptfs_kthread_ctl.mux);
+                printk(KERN_ERR "%s: We are in the middle of shutting down; "
+                       "aborting privileged request to open lower file\n",
+                        __func__);
+                goto out_free;
+        }
+        list_add_tail(&req->kthread_ctl_list, &ecryptfs_kthread_ctl.req_list);
+        mutex_unlock(&ecryptfs_kthread_ctl.mux);
+        wake_up(&ecryptfs_kthread_ctl.wait);
+        wait_event(req->wait, (req->flags != 0));
+        mutex_lock(&req->mux);
+        BUG_ON(req->flags == 0);
+        if (req->flags & ECRYPTFS_REQ_DROPPED
+            || req->flags & ECRYPTFS_REQ_ZOMBIE) {
+                rc = -EIO;
+                printk(KERN_WARNING "%s: Privileged open request dropped\n",
+                       __func__);
+                goto out_unlock;
+        }
+        if (IS_ERR(*req->lower_file)) {
+                rc = PTR_ERR(*req->lower_file);
+                dget(lower_dentry);
+                mntget(lower_mnt);
+                (*lower_file) = dentry_open(lower_dentry, lower_mnt,
+                                            (O_RDONLY | O_LARGEFILE));
+                if (IS_ERR(*lower_file)) {
+                        rc = PTR_ERR(*req->lower_file);
+                        (*lower_file) = NULL;
+                        printk(KERN_WARNING "%s: Error attempting privileged "
+                               "open of lower file with either RW or RO "
+                               "perms; rc = [%d]. Giving up.\n",
+                               __func__, rc);
+                }
+        }
+out_unlock:
+        mutex_unlock(&req->mux);
+out_free:
+        kmem_cache_free(ecryptfs_open_req_cache, req);
+out:
+        return rc;
+}
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index d603631601eb..f36ab2feea28 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -130,26 +130,12 @@ static int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
                         ecryptfs_dentry_to_lower_mnt(ecryptfs_dentry);
 
                 lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
-                /* Corresponding dput() and mntput() are done when the
-                 * persistent file is fput() when the eCryptfs inode
-                 * is destroyed. */
-                dget(lower_dentry);
-                mntget(lower_mnt);
-                inode_info->lower_file = dentry_open(lower_dentry,
-                                                     lower_mnt,
-                                                     (O_RDWR | O_LARGEFILE));
-                if (IS_ERR(inode_info->lower_file)) {
-                        dget(lower_dentry);
-                        mntget(lower_mnt);
-                        inode_info->lower_file = dentry_open(lower_dentry,
-                                                             lower_mnt,
-                                                             (O_RDONLY
-                                                              | O_LARGEFILE));
-                }
-                if (IS_ERR(inode_info->lower_file)) {
+                rc = ecryptfs_privileged_open(&inode_info->lower_file,
+                                                     lower_dentry, lower_mnt);
+                if (rc || IS_ERR(inode_info->lower_file)) {
                         printk(KERN_ERR "Error opening lower persistent file "
-                               "for lower_dentry [0x%p] and lower_mnt [0x%p]\n",
-                               lower_dentry, lower_mnt);
+                               "for lower_dentry [0x%p] and lower_mnt [0x%p]; "
+                               "rc = [%d]\n", lower_dentry, lower_mnt, rc);
                         rc = PTR_ERR(inode_info->lower_file);
                         inode_info->lower_file = NULL;
                 }
@@ -679,6 +665,11 @@ static struct ecryptfs_cache_info {
                 .name = "ecryptfs_key_tfm_cache",
                 .size = sizeof(struct ecryptfs_key_tfm),
         },
+        {
+                .cache = &ecryptfs_open_req_cache,
+                .name = "ecryptfs_open_req_cache",
+                .size = sizeof(struct ecryptfs_open_req),
+        },
 };
 
 static void ecryptfs_free_kmem_caches(void)
@@ -795,11 +786,17 @@ static int __init ecryptfs_init(void)
                 printk(KERN_ERR "sysfs registration failed\n");
                 goto out_unregister_filesystem;
         }
+        rc = ecryptfs_init_kthread();
+        if (rc) {
+                printk(KERN_ERR "%s: kthread initialization failed; "
+                       "rc = [%d]\n", __func__, rc);
+                goto out_do_sysfs_unregistration;
+        }
         rc = ecryptfs_init_messaging(ecryptfs_transport);
         if (rc) {
-                ecryptfs_printk(KERN_ERR, "Failure occured while attempting to "
+                printk(KERN_ERR "Failure occured while attempting to "
                                 "initialize the eCryptfs netlink socket\n");
-                goto out_do_sysfs_unregistration;
+                goto out_destroy_kthread;
         }
         rc = ecryptfs_init_crypto();
         if (rc) {
@@ -814,6 +811,8 @@ static int __init ecryptfs_init(void)
         goto out;
 out_release_messaging:
         ecryptfs_release_messaging(ecryptfs_transport);
+out_destroy_kthread:
+        ecryptfs_destroy_kthread();
 out_do_sysfs_unregistration:
         do_sysfs_unregistration();
 out_unregister_filesystem:
@@ -833,6 +832,7 @@ static void __exit ecryptfs_exit(void)
                 printk(KERN_ERR "Failure whilst attempting to destroy crypto; "
                        "rc = [%d]\n", rc);
         ecryptfs_release_messaging(ecryptfs_transport);
+        ecryptfs_destroy_kthread();
         do_sysfs_unregistration();
         unregister_filesystem(&ecryptfs_fs_type);
         ecryptfs_free_kmem_caches();