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eCryptfs: Make all miscdev functions use daemon ptr in file private_data

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Now that a pointer to a valid struct ecryptfs_daemon is stored in the
private_data of an opened /dev/ecryptfs file, the remaining miscdev
functions can utilize the pointer rather than looking up the
ecryptfs_daemon at the beginning of each operation.

The security model of /dev/ecryptfs is simplified a little bit with this
patch. Upon opening /dev/ecryptfs, a per-user ecryptfs_daemon is
registered. Another daemon cannot be registered for that user until the
last file reference is released. During the lifetime of the
ecryptfs_daemon, access checks are not performed on the /dev/ecryptfs
operations because it is assumed that the application securely handles
the opened file descriptor and does not unintentionally leak it to
processes that are not trusted.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
This commit is contained in:
Tyler Hicks
2012-06-11 09:47:47 -07:00
parent 5669688665
commit 2ecaf55db6
3 changed files with 47 additions and 172 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/ecryptfs/miscdev.c
+26 -72
View File
@@ -33,7 +33,7 @@ static atomic_t ecryptfs_num_miscdev_opens;
/**
* ecryptfs_miscdev_poll
* @file: dev file (ignored)
* @file: dev file
* @pt: dev poll table (ignored)
*
* Returns the poll mask
@@ -41,20 +41,10 @@ static atomic_t ecryptfs_num_miscdev_opens;
static unsigned int
ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
{
struct ecryptfs_daemon *daemon;
struct ecryptfs_daemon *daemon = file->private_data;
unsigned int mask = 0;
uid_t euid = current_euid();
int rc;
mutex_lock(&ecryptfs_daemon_hash_mux);
/* TODO: Just use file->private_data? */
rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
if (rc || !daemon) {
mutex_unlock(&ecryptfs_daemon_hash_mux);
return -EINVAL;
}
mutex_lock(&daemon->mux);
mutex_unlock(&ecryptfs_daemon_hash_mux);
if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
printk(KERN_WARNING "%s: Attempt to poll on zombified "
"daemon\n", __func__);
@@ -79,7 +69,7 @@ out_unlock_daemon:
/**
* ecryptfs_miscdev_open
* @inode: inode of miscdev handle (ignored)
* @file: file for miscdev handle (ignored)
* @file: file for miscdev handle
*
* Returns zero on success; non-zero otherwise
*/
@@ -87,7 +77,6 @@ static int
ecryptfs_miscdev_open(struct inode *inode, struct file *file)
{
struct ecryptfs_daemon *daemon = NULL;
uid_t euid = current_euid();
int rc;
mutex_lock(&ecryptfs_daemon_hash_mux);
@@ -98,30 +87,20 @@ ecryptfs_miscdev_open(struct inode *inode, struct file *file)
"count; rc = [%d]\n", __func__, rc);
goto out_unlock_daemon_list;
}
rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
if (rc || !daemon) {
rc = ecryptfs_spawn_daemon(&daemon, euid, current_user_ns(),
task_pid(current));
if (rc) {
printk(KERN_ERR "%s: Error attempting to spawn daemon; "
"rc = [%d]\n", __func__, rc);
goto out_module_put_unlock_daemon_list;
}
rc = ecryptfs_find_daemon_by_euid(&daemon);
if (!rc) {
rc = -EINVAL;
goto out_unlock_daemon_list;
}
rc = ecryptfs_spawn_daemon(&daemon, file);
if (rc) {
printk(KERN_ERR "%s: Error attempting to spawn daemon; "
"rc = [%d]\n", __func__, rc);
goto out_module_put_unlock_daemon_list;
}
mutex_lock(&daemon->mux);
if (daemon->pid != task_pid(current)) {
rc = -EINVAL;
printk(KERN_ERR "%s: pid [0x%p] has registered with euid [%d], "
"but pid [0x%p] has attempted to open the handle "
"instead\n", __func__, daemon->pid, daemon->euid,
task_pid(current));
goto out_unlock_daemon;
}
if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
rc = -EBUSY;
printk(KERN_ERR "%s: Miscellaneous device handle may only be "
"opened once per daemon; pid [0x%p] already has this "
"handle open\n", __func__, daemon->pid);
goto out_unlock_daemon;
}
daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
@@ -140,7 +119,7 @@ out_unlock_daemon_list:
/**
* ecryptfs_miscdev_release
* @inode: inode of fs/ecryptfs/euid handle (ignored)
* @file: file for fs/ecryptfs/euid handle (ignored)
* @file: file for fs/ecryptfs/euid handle
*
* This keeps the daemon registered until the daemon sends another
* ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
@@ -150,20 +129,18 @@ out_unlock_daemon_list:
static int
ecryptfs_miscdev_release(struct inode *inode, struct file *file)
{
struct ecryptfs_daemon *daemon = NULL;
uid_t euid = current_euid();
struct ecryptfs_daemon *daemon = file->private_data;
int rc;
mutex_lock(&ecryptfs_daemon_hash_mux);
rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
if (rc || !daemon)
daemon = file->private_data;
mutex_lock(&daemon->mux);
BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
atomic_dec(&ecryptfs_num_miscdev_opens);
mutex_unlock(&daemon->mux);
mutex_lock(&ecryptfs_daemon_hash_mux);
rc = ecryptfs_exorcise_daemon(daemon);
mutex_unlock(&ecryptfs_daemon_hash_mux);
if (rc) {
printk(KERN_CRIT "%s: Fatal error whilst attempting to "
"shut down daemon; rc = [%d]. Please report this "
@@ -171,7 +148,6 @@ ecryptfs_miscdev_release(struct inode *inode, struct file *file)
BUG();
}
module_put(THIS_MODULE);
mutex_unlock(&ecryptfs_daemon_hash_mux);
return rc;
}
@@ -248,7 +224,7 @@ int ecryptfs_send_miscdev(char *data, size_t data_size,
/**
* ecryptfs_miscdev_read - format and send message from queue
* @file: fs/ecryptfs/euid miscdevfs handle (ignored)
* @file: miscdevfs handle
* @buf: User buffer into which to copy the next message on the daemon queue
* @count: Amount of space available in @buf
* @ppos: Offset in file (ignored)
@@ -262,43 +238,27 @@ static ssize_t
ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
loff_t *ppos)
{
struct ecryptfs_daemon *daemon;
struct ecryptfs_daemon *daemon = file->private_data;
struct ecryptfs_msg_ctx *msg_ctx;
size_t packet_length_size;
char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
size_t i;
size_t total_length;
uid_t euid = current_euid();
int rc;
mutex_lock(&ecryptfs_daemon_hash_mux);
/* TODO: Just use file->private_data? */
rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
if (rc || !daemon) {
mutex_unlock(&ecryptfs_daemon_hash_mux);
return -EINVAL;
}
mutex_lock(&daemon->mux);
if (task_pid(current) != daemon->pid) {
mutex_unlock(&daemon->mux);
mutex_unlock(&ecryptfs_daemon_hash_mux);
return -EPERM;
}
if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
rc = 0;
mutex_unlock(&ecryptfs_daemon_hash_mux);
printk(KERN_WARNING "%s: Attempt to read from zombified "
"daemon\n", __func__);
goto out_unlock_daemon;
}
if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
rc = 0;
mutex_unlock(&ecryptfs_daemon_hash_mux);
goto out_unlock_daemon;
}
/* This daemon will not go away so long as this flag is set */
daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
mutex_unlock(&ecryptfs_daemon_hash_mux);
check_list:
if (list_empty(&daemon->msg_ctx_out_queue)) {
mutex_unlock(&daemon->mux);
@@ -382,16 +342,12 @@ out_unlock_daemon:
* ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
* @data: Bytes comprising struct ecryptfs_message
* @data_size: sizeof(struct ecryptfs_message) + data len
* @euid: Effective user id of miscdevess sending the miscdev response
* @user_ns: The namespace in which @euid applies
* @pid: Miscdevess id of miscdevess sending the miscdev response
* @seq: Sequence number for miscdev response packet
*
* Returns zero on success; non-zero otherwise
*/
static int ecryptfs_miscdev_response(char *data, size_t data_size,
uid_t euid, struct user_namespace *user_ns,
struct pid *pid, u32 seq)
static int ecryptfs_miscdev_response(struct ecryptfs_daemon *daemon, char *data,
size_t data_size, u32 seq)
{
struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
int rc;
@@ -403,7 +359,7 @@ static int ecryptfs_miscdev_response(char *data, size_t data_size,
rc = -EINVAL;
goto out;
}
rc = ecryptfs_process_response(msg, euid, user_ns, pid, seq);
rc = ecryptfs_process_response(daemon, msg, seq);
if (rc)
printk(KERN_ERR
"Error processing response message; rc = [%d]\n", rc);
@@ -413,7 +369,7 @@ out:
/**
* ecryptfs_miscdev_write - handle write to daemon miscdev handle
* @file: File for misc dev handle (ignored)
* @file: File for misc dev handle
* @buf: Buffer containing user data
* @count: Amount of data in @buf
* @ppos: Pointer to offset in file (ignored)
@@ -428,7 +384,6 @@ ecryptfs_miscdev_write(struct file *file, const char __user *buf,
u32 seq;
size_t packet_size, packet_size_length;
char *data;
uid_t euid = current_euid();
unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
ssize_t rc;
@@ -488,10 +443,9 @@ memdup:
}
memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
seq = be32_to_cpu(counter_nbo);
rc = ecryptfs_miscdev_response(
rc = ecryptfs_miscdev_response(file->private_data,
&data[PKT_LEN_OFFSET + packet_size_length],
packet_size, euid, current_user_ns(),
task_pid(current), seq);
packet_size, seq);
if (rc) {
printk(KERN_WARNING "%s: Failed to deliver miscdev "
"response to requesting operation; rc = [%zd]\n",