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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>
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Tyler Hicks committed Jul 8, 2012
1 parent 5669688 commit 2ecaf55
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Showing 3 changed files with 47 additions and 172 deletions.
16 changes: 5 additions & 11 deletions fs/ecryptfs/ecryptfs_kernel.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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,
Expand All @@ -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,
Expand Down
105 changes: 16 additions & 89 deletions fs/ecryptfs/messaging.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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;
}
Expand All @@ -137,18 +135,15 @@ int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon, uid_t euid,
/**
* 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
*
* 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;

Expand All @@ -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;
}
Expand All @@ -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;
}
Expand All @@ -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:
Expand All @@ -219,8 +202,6 @@ int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
* 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
Expand All @@ -239,16 +220,11 @@ int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
*
* 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) {
Expand All @@ -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 "
Expand All @@ -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:
Expand All @@ -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);
Expand Down
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