[PATCH 3/3] eCryptfs: Make all miscdev functions use daemon ptr in file private_data

From: Tyler Hicks
Date: Tue Jun 12 2012 - 20:06:17 EST

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@xxxxxxxxxxxxx>
Cc: Sasha Levin <levinsasha928@xxxxxxxxx>
---
fs/ecryptfs/ecryptfs_kernel.h | 16 ++-----
fs/ecryptfs/messaging.c | 105 +++++++----------------------------------
fs/ecryptfs/miscdev.c | 98 ++++++++++----------------------------
3 files changed, 47 insertions(+), 172 deletions(-)

diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 01a1f85..0deb4f2 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -392,10 +392,7 @@ struct ecryptfs_daemon {
#define ECRYPTFS_DAEMON_MISCDEV_OPEN 0x00000008
u32 flags;
u32 num_queued_msg_ctx;
- struct pid *pid;
- uid_t euid;
- struct user_namespace *user_ns;
- struct task_struct *task;
+ struct file *file;
struct mutex mux;
struct list_head msg_ctx_out_queue;
wait_queue_head_t wait;
@@ -619,9 +616,8 @@ int
ecryptfs_setxattr(struct dentry *dentry, const char *name, const void *value,
size_t size, int flags);
int ecryptfs_read_xattr_region(char *page_virt, struct inode *ecryptfs_inode);
-int ecryptfs_process_response(struct ecryptfs_message *msg, uid_t euid,
- struct user_namespace *user_ns, struct pid *pid,
- u32 seq);
+int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
+ struct ecryptfs_message *msg, u32 seq);
int ecryptfs_send_message(char *data, int data_len,
struct ecryptfs_msg_ctx **msg_ctx);
int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
@@ -666,8 +662,7 @@ int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
struct inode *ecryptfs_inode);
struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index);
int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon);
-int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon, uid_t euid,
- struct user_namespace *user_ns);
+int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon);
int ecryptfs_parse_packet_length(unsigned char *data, size_t *size,
size_t *length_size);
int ecryptfs_write_packet_length(char *dest, size_t size,
@@ -679,8 +674,7 @@ int ecryptfs_send_miscdev(char *data, size_t data_size,
u16 msg_flags, struct ecryptfs_daemon *daemon);
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);
+ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file);
int ecryptfs_init_kthread(void);
void ecryptfs_destroy_kthread(void);
int ecryptfs_privileged_open(struct file **lower_file,
diff --git a/fs/ecryptfs/messaging.c b/fs/ecryptfs/messaging.c
index c11911d..b29bb8b 100644
--- a/fs/ecryptfs/messaging.c
+++ b/fs/ecryptfs/messaging.c
@@ -32,8 +32,8 @@ static struct mutex ecryptfs_msg_ctx_lists_mux;
static struct hlist_head *ecryptfs_daemon_hash;
struct mutex ecryptfs_daemon_hash_mux;
static int ecryptfs_hash_bits;
-#define ecryptfs_uid_hash(uid) \
- hash_long((unsigned long)uid, ecryptfs_hash_bits)
+#define ecryptfs_current_euid_hash(uid) \
+ hash_long((unsigned long)current_euid(), ecryptfs_hash_bits)

static u32 ecryptfs_msg_counter;
static struct ecryptfs_msg_ctx *ecryptfs_msg_ctx_arr;
@@ -105,26 +105,24 @@ void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx)

/**
* ecryptfs_find_daemon_by_euid
- * @euid: The effective user id which maps to the desired daemon id
- * @user_ns: The namespace in which @euid applies
* @daemon: If return value is zero, points to the desired daemon pointer
*
* Must be called with ecryptfs_daemon_hash_mux held.
*
- * Search the hash list for the given user id.
+ * Search the hash list for the current effective user id.
*
* Returns zero if the user id exists in the list; non-zero otherwise.
*/
-int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon, uid_t euid,
- struct user_namespace *user_ns)
+int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
{
struct hlist_node *elem;
int rc;

hlist_for_each_entry(*daemon, elem,
- &ecryptfs_daemon_hash[ecryptfs_uid_hash(euid)],
- euid_chain) {
- if ((*daemon)->euid == euid && (*daemon)->user_ns == user_ns) {
+ &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()],
+ euid_chain) {
+ if ((*daemon)->file->f_cred->euid == current_euid() &&
+ (*daemon)->file->f_cred->user_ns == current_user_ns()) {
rc = 0;
goto out;
}
@@ -137,9 +135,7 @@ out:
/**
* ecryptfs_spawn_daemon - Create and initialize a new daemon struct
* @daemon: Pointer to set to newly allocated daemon struct
- * @euid: Effective user id for the daemon
- * @user_ns: The namespace in which @euid applies
- * @pid: Process id for the daemon
+ * @file: File used when opening /dev/ecryptfs
*
* Must be called ceremoniously while in possession of
* ecryptfs_sacred_daemon_hash_mux
@@ -147,8 +143,7 @@ out:
* Returns zero on success; non-zero otherwise
*/
int
-ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, uid_t euid,
- struct user_namespace *user_ns, struct pid *pid)
+ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
{
int rc = 0;

@@ -159,16 +154,13 @@ ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, uid_t euid,
"GFP_KERNEL memory\n", __func__, sizeof(**daemon));
goto out;
}
- (*daemon)->euid = euid;
- (*daemon)->user_ns = get_user_ns(user_ns);
- (*daemon)->pid = get_pid(pid);
- (*daemon)->task = current;
+ (*daemon)->file = file;
mutex_init(&(*daemon)->mux);
INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
init_waitqueue_head(&(*daemon)->wait);
(*daemon)->num_queued_msg_ctx = 0;
hlist_add_head(&(*daemon)->euid_chain,
- &ecryptfs_daemon_hash[ecryptfs_uid_hash(euid)]);
+ &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
out:
return rc;
}
@@ -188,9 +180,6 @@ int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
|| (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
rc = -EBUSY;
- printk(KERN_WARNING "%s: Attempt to destroy daemon with pid "
- "[0x%p], but it is in the midst of a read or a poll\n",
- __func__, daemon->pid);
mutex_unlock(&daemon->mux);
goto out;
}
@@ -203,12 +192,6 @@ int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
}
hlist_del(&daemon->euid_chain);
- if (daemon->task)
- wake_up_process(daemon->task);
- if (daemon->pid)
- put_pid(daemon->pid);
- if (daemon->user_ns)
- put_user_ns(daemon->user_ns);
mutex_unlock(&daemon->mux);
kzfree(daemon);
out:
@@ -219,8 +202,6 @@ out:
* ecryptfs_process_reponse
* @msg: The ecryptfs message received; the caller should sanity check
* msg->data_len and free the memory
- * @pid: The process ID of the userspace application that sent the
- * message
* @seq: The sequence number of the message; must match the sequence
* number for the existing message context waiting for this
* response
@@ -239,16 +220,11 @@ out:
*
* Returns zero on success; non-zero otherwise
*/
-int ecryptfs_process_response(struct ecryptfs_message *msg, uid_t euid,
- struct user_namespace *user_ns, struct pid *pid,
- u32 seq)
+int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
+ struct ecryptfs_message *msg, u32 seq)
{
- struct ecryptfs_daemon *uninitialized_var(daemon);
struct ecryptfs_msg_ctx *msg_ctx;
size_t msg_size;
- struct nsproxy *nsproxy;
- struct user_namespace *tsk_user_ns;
- uid_t ctx_euid;
int rc;

if (msg->index >= ecryptfs_message_buf_len) {
@@ -261,51 +237,6 @@ int ecryptfs_process_response(struct ecryptfs_message *msg, uid_t euid,
}
msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
mutex_lock(&msg_ctx->mux);
- mutex_lock(&ecryptfs_daemon_hash_mux);
- rcu_read_lock();
- nsproxy = task_nsproxy(msg_ctx->task);
- if (nsproxy == NULL) {
- rc = -EBADMSG;
- printk(KERN_ERR "%s: Receiving process is a zombie. Dropping "
- "message.\n", __func__);
- rcu_read_unlock();
- mutex_unlock(&ecryptfs_daemon_hash_mux);
- goto wake_up;
- }
- tsk_user_ns = __task_cred(msg_ctx->task)->user_ns;
- ctx_euid = task_euid(msg_ctx->task);
- rc = ecryptfs_find_daemon_by_euid(&daemon, ctx_euid, tsk_user_ns);
- rcu_read_unlock();
- mutex_unlock(&ecryptfs_daemon_hash_mux);
- if (rc) {
- rc = -EBADMSG;
- printk(KERN_WARNING "%s: User [%d] received a "
- "message response from process [0x%p] but does "
- "not have a registered daemon\n", __func__,
- ctx_euid, pid);
- goto wake_up;
- }
- if (ctx_euid != euid) {
- rc = -EBADMSG;
- printk(KERN_WARNING "%s: Received message from user "
- "[%d]; expected message from user [%d]\n", __func__,
- euid, ctx_euid);
- goto unlock;
- }
- if (tsk_user_ns != user_ns) {
- rc = -EBADMSG;
- printk(KERN_WARNING "%s: Received message from user_ns "
- "[0x%p]; expected message from user_ns [0x%p]\n",
- __func__, user_ns, tsk_user_ns);
- goto unlock;
- }
- if (daemon->pid != pid) {
- rc = -EBADMSG;
- printk(KERN_ERR "%s: User [%d] sent a message response "
- "from an unrecognized process [0x%p]\n",
- __func__, ctx_euid, pid);
- goto unlock;
- }
if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
rc = -EINVAL;
printk(KERN_WARNING "%s: Desired context element is not "
@@ -328,9 +259,8 @@ int ecryptfs_process_response(struct ecryptfs_message *msg, uid_t euid,
}
memcpy(msg_ctx->msg, msg, msg_size);
msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
- rc = 0;
-wake_up:
wake_up_process(msg_ctx->task);
+ rc = 0;
unlock:
mutex_unlock(&msg_ctx->mux);
out:
@@ -352,14 +282,11 @@ ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
struct ecryptfs_msg_ctx **msg_ctx)
{
struct ecryptfs_daemon *daemon;
- uid_t euid = current_euid();
int rc;

- rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
+ rc = ecryptfs_find_daemon_by_euid(&daemon);
if (rc || !daemon) {
rc = -ENOTCONN;
- printk(KERN_ERR "%s: User [%d] does not have a daemon "
- "registered\n", __func__, euid);
goto out;
}
mutex_lock(&ecryptfs_msg_ctx_lists_mux);
diff --git a/fs/ecryptfs/miscdev.c b/fs/ecryptfs/miscdev.c
index 2cd9c3f..358156b 100644
--- a/fs/ecryptfs/miscdev.c
+++ b/fs/ecryptfs/miscdev.c
@@ -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;
- }
- }
- mutex_lock(&daemon->mux);
- if (daemon->pid != task_pid(current)) {
+ rc = ecryptfs_find_daemon_by_euid(&daemon);
+ if (!rc) {
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;
+ 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->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;
}

@@ -247,7 +223,7 @@ out_unlock:

/**
* 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)
@@ -261,43 +237,27 @@ 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);
@@ -381,16 +341,12 @@ 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;
@@ -402,7 +358,7 @@ 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);
@@ -412,7 +368,7 @@ 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)
@@ -427,7 +383,6 @@ 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;

@@ -487,10 +442,9 @@ 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",
--
1.7.9.5

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