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linux/fs/ecryptfs/miscdev.c
Arnd Bergmann 6038f373a3 llseek: automatically add .llseek fop 
All file_operations should get a .llseek operation so we can make
nonseekable_open the default for future file operations without a
.llseek pointer.

The three cases that we can automatically detect are no_llseek, seq_lseek
and default_llseek. For cases where we can we can automatically prove that
the file offset is always ignored, we use noop_llseek, which maintains
the current behavior of not returning an error from a seek.

New drivers should normally not use noop_llseek but instead use no_llseek
and call nonseekable_open at open time.  Existing drivers can be converted
to do the same when the maintainer knows for certain that no user code
relies on calling seek on the device file.

The generated code is often incorrectly indented and right now contains
comments that clarify for each added line why a specific variant was
chosen. In the version that gets submitted upstream, the comments will
be gone and I will manually fix the indentation, because there does not
seem to be a way to do that using coccinelle.

Some amount of new code is currently sitting in linux-next that should get
the same modifications, which I will do at the end of the merge window.

Many thanks to Julia Lawall for helping me learn to write a semantic
patch that does all this.

===== begin semantic patch =====
// This adds an llseek= method to all file operations,
// as a preparation for making no_llseek the default.
//
// The rules are
// - use no_llseek explicitly if we do nonseekable_open
// - use seq_lseek for sequential files
// - use default_llseek if we know we access f_pos
// - use noop_llseek if we know we don't access f_pos,
//   but we still want to allow users to call lseek
//
@ open1 exists @
identifier nested_open;
@@
nested_open(...)
{
<+...
nonseekable_open(...)
...+>
}

@ open exists@
identifier open_f;
identifier i, f;
identifier open1.nested_open;
@@
int open_f(struct inode *i, struct file *f)
{
<+...
(
nonseekable_open(...)
|
nested_open(...)
)
...+>
}

@ read disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
<+...
(
   *off = E
|
   *off += E
|
   func(..., off, ...)
|
   E = *off
)
...+>
}

@ read_no_fpos disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
... when != off
}

@ write @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
<+...
(
  *off = E
|
  *off += E
|
  func(..., off, ...)
|
  E = *off
)
...+>
}

@ write_no_fpos @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
... when != off
}

@ fops0 @
identifier fops;
@@
struct file_operations fops = {
 ...
};

@ has_llseek depends on fops0 @
identifier fops0.fops;
identifier llseek_f;
@@
struct file_operations fops = {
...
 .llseek = llseek_f,
...
};

@ has_read depends on fops0 @
identifier fops0.fops;
identifier read_f;
@@
struct file_operations fops = {
...
 .read = read_f,
...
};

@ has_write depends on fops0 @
identifier fops0.fops;
identifier write_f;
@@
struct file_operations fops = {
...
 .write = write_f,
...
};

@ has_open depends on fops0 @
identifier fops0.fops;
identifier open_f;
@@
struct file_operations fops = {
...
 .open = open_f,
...
};

// use no_llseek if we call nonseekable_open
////////////////////////////////////////////
@ nonseekable1 depends on !has_llseek && has_open @
identifier fops0.fops;
identifier nso ~= "nonseekable_open";
@@
struct file_operations fops = {
...  .open = nso, ...
+.llseek = no_llseek, /* nonseekable */
};

@ nonseekable2 depends on !has_llseek @
identifier fops0.fops;
identifier open.open_f;
@@
struct file_operations fops = {
...  .open = open_f, ...
+.llseek = no_llseek, /* open uses nonseekable */
};

// use seq_lseek for sequential files
/////////////////////////////////////
@ seq depends on !has_llseek @
identifier fops0.fops;
identifier sr ~= "seq_read";
@@
struct file_operations fops = {
...  .read = sr, ...
+.llseek = seq_lseek, /* we have seq_read */
};

// use default_llseek if there is a readdir
///////////////////////////////////////////
@ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier readdir_e;
@@
// any other fop is used that changes pos
struct file_operations fops = {
... .readdir = readdir_e, ...
+.llseek = default_llseek, /* readdir is present */
};

// use default_llseek if at least one of read/write touches f_pos
/////////////////////////////////////////////////////////////////
@ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read.read_f;
@@
// read fops use offset
struct file_operations fops = {
... .read = read_f, ...
+.llseek = default_llseek, /* read accesses f_pos */
};

@ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write.write_f;
@@
// write fops use offset
struct file_operations fops = {
... .write = write_f, ...
+	.llseek = default_llseek, /* write accesses f_pos */
};

// Use noop_llseek if neither read nor write accesses f_pos
///////////////////////////////////////////////////////////

@ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
identifier write_no_fpos.write_f;
@@
// write fops use offset
struct file_operations fops = {
...
 .write = write_f,
 .read = read_f,
...
+.llseek = noop_llseek, /* read and write both use no f_pos */
};

@ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write_no_fpos.write_f;
@@
struct file_operations fops = {
... .write = write_f, ...
+.llseek = noop_llseek, /* write uses no f_pos */
};

@ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
@@
struct file_operations fops = {
... .read = read_f, ...
+.llseek = noop_llseek, /* read uses no f_pos */
};

@ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
@@
struct file_operations fops = {
...
+.llseek = noop_llseek, /* no read or write fn */
};
===== End semantic patch =====

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Julia Lawall <julia@diku.dk>
Cc: Christoph Hellwig <hch@infradead.org>
2010-10-15 15:53:27 +02:00

528 lines
16 KiB
C
Raw Blame History

/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 2008 International Business Machines Corp.
* Author(s): Michael A. Halcrow <mhalcrow@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 version
* 2 as published by the Free Software Foundation.
*
* 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/fs.h>
#include <linux/hash.h>
#include <linux/random.h>
#include <linux/miscdevice.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/module.h>
#include "ecryptfs_kernel.h"
static atomic_t ecryptfs_num_miscdev_opens;
/**
* ecryptfs_miscdev_poll
* @file: dev file (ignored)
* @pt: dev poll table (ignored)
*
* Returns the poll mask
*/
static unsigned int
ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
{
struct ecryptfs_daemon *daemon;
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());
BUG_ON(rc || !daemon);
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__);
goto out_unlock_daemon;
}
if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
goto out_unlock_daemon;
if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
goto out_unlock_daemon;
daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
mutex_unlock(&daemon->mux);
poll_wait(file, &daemon->wait, pt);
mutex_lock(&daemon->mux);
if (!list_empty(&daemon->msg_ctx_out_queue))
mask |= POLLIN | POLLRDNORM;
out_unlock_daemon:
daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
mutex_unlock(&daemon->mux);
return mask;
}
/**
* ecryptfs_miscdev_open
* @inode: inode of miscdev handle (ignored)
* @file: file for miscdev handle (ignored)
*
* Returns zero on success; non-zero otherwise
*/
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);
rc = try_module_get(THIS_MODULE);
if (rc == 0) {
rc = -EIO;
printk(KERN_ERR "%s: Error attempting to increment module use "
"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 = -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;
atomic_inc(&ecryptfs_num_miscdev_opens);
out_unlock_daemon:
mutex_unlock(&daemon->mux);
out_module_put_unlock_daemon_list:
if (rc)
module_put(THIS_MODULE);
out_unlock_daemon_list:
mutex_unlock(&ecryptfs_daemon_hash_mux);
return rc;
}
/**
* ecryptfs_miscdev_release
* @inode: inode of fs/ecryptfs/euid handle (ignored)
* @file: file for fs/ecryptfs/euid handle (ignored)
*
* This keeps the daemon registered until the daemon sends another
* ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
*
* Returns zero on success; non-zero otherwise
*/
static int
ecryptfs_miscdev_release(struct inode *inode, struct file *file)
{
struct ecryptfs_daemon *daemon = NULL;
uid_t euid = current_euid();
int rc;
mutex_lock(&ecryptfs_daemon_hash_mux);
rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
BUG_ON(rc || !daemon);
mutex_lock(&daemon->mux);
BUG_ON(daemon->pid != task_pid(current));
BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
atomic_dec(&ecryptfs_num_miscdev_opens);
mutex_unlock(&daemon->mux);
rc = ecryptfs_exorcise_daemon(daemon);
if (rc) {
printk(KERN_CRIT "%s: Fatal error whilst attempting to "
"shut down daemon; rc = [%d]. Please report this "
"bug.\n", __func__, rc);
BUG();
}
module_put(THIS_MODULE);
mutex_unlock(&ecryptfs_daemon_hash_mux);
return rc;
}
/**
* ecryptfs_send_miscdev
* @data: Data to send to daemon; may be NULL
* @data_size: Amount of data to send to daemon
* @msg_ctx: Message context, which is used to handle the reply. If
* this is NULL, then we do not expect a reply.
* @msg_type: Type of message
* @msg_flags: Flags for message
* @daemon: eCryptfs daemon object
*
* Add msg_ctx to queue and then, if it exists, notify the blocked
* miscdevess about the data being available. Must be called with
* ecryptfs_daemon_hash_mux held.
*
* Returns zero on success; non-zero otherwise
*/
int ecryptfs_send_miscdev(char *data, size_t data_size,
struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
u16 msg_flags, struct ecryptfs_daemon *daemon)
{
int rc = 0;
mutex_lock(&msg_ctx->mux);
msg_ctx->msg = kmalloc((sizeof(*msg_ctx->msg) + data_size),
GFP_KERNEL);
if (!msg_ctx->msg) {
rc = -ENOMEM;
printk(KERN_ERR "%s: Out of memory whilst attempting "
"to kmalloc(%zd, GFP_KERNEL)\n", __func__,
(sizeof(*msg_ctx->msg) + data_size));
goto out_unlock;
}
msg_ctx->msg->index = msg_ctx->index;
msg_ctx->msg->data_len = data_size;
msg_ctx->type = msg_type;
memcpy(msg_ctx->msg->data, data, data_size);
msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
mutex_lock(&daemon->mux);
list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
daemon->num_queued_msg_ctx++;
wake_up_interruptible(&daemon->wait);
mutex_unlock(&daemon->mux);
out_unlock:
mutex_unlock(&msg_ctx->mux);
return rc;
}
/**
* ecryptfs_miscdev_read - format and send message from queue
* @file: fs/ecryptfs/euid miscdevfs handle (ignored)
* @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)
*
* Pulls the most recent message from the daemon queue, formats it for
* being sent via a miscdevfs handle, and copies it into @buf
*
* Returns the number of bytes copied into the user buffer
*/
static ssize_t
ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
loff_t *ppos)
{
struct ecryptfs_daemon *daemon;
struct ecryptfs_msg_ctx *msg_ctx;
size_t packet_length_size;
char packet_length[3];
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());
BUG_ON(rc || !daemon);
mutex_lock(&daemon->mux);
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);
rc = wait_event_interruptible(
daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
mutex_lock(&daemon->mux);
if (rc < 0) {
rc = 0;
goto out_unlock_daemon;
}
}
if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
rc = 0;
goto out_unlock_daemon;
}
if (list_empty(&daemon->msg_ctx_out_queue)) {
/* Something else jumped in since the
* wait_event_interruptable() and removed the
* message from the queue; try again */
goto check_list;
}
BUG_ON(euid != daemon->euid);
BUG_ON(current_user_ns() != daemon->user_ns);
BUG_ON(task_pid(current) != daemon->pid);
msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
struct ecryptfs_msg_ctx, daemon_out_list);
BUG_ON(!msg_ctx);
mutex_lock(&msg_ctx->mux);
if (msg_ctx->msg) {
rc = ecryptfs_write_packet_length(packet_length,
msg_ctx->msg_size,
&packet_length_size);
if (rc) {
rc = 0;
printk(KERN_WARNING "%s: Error writing packet length; "
"rc = [%d]\n", __func__, rc);
goto out_unlock_msg_ctx;
}
} else {
packet_length_size = 0;
msg_ctx->msg_size = 0;
}
/* miscdevfs packet format:
* Octet 0: Type
* Octets 1-4: network byte order msg_ctx->counter
* Octets 5-N0: Size of struct ecryptfs_message to follow
* Octets N0-N1: struct ecryptfs_message (including data)
*
* Octets 5-N1 not written if the packet type does not
* include a message */
total_length = (1 + 4 + packet_length_size + msg_ctx->msg_size);
if (count < total_length) {
rc = 0;
printk(KERN_WARNING "%s: Only given user buffer of "
"size [%zd], but we need [%zd] to read the "
"pending message\n", __func__, count, total_length);
goto out_unlock_msg_ctx;
}
rc = -EFAULT;
if (put_user(msg_ctx->type, buf))
goto out_unlock_msg_ctx;
if (put_user(cpu_to_be32(msg_ctx->counter), (__be32 __user *)(buf + 1)))
goto out_unlock_msg_ctx;
i = 5;
if (msg_ctx->msg) {
if (copy_to_user(&buf[i], packet_length, packet_length_size))
goto out_unlock_msg_ctx;
i += packet_length_size;
if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
goto out_unlock_msg_ctx;
i += msg_ctx->msg_size;
}
rc = i;
list_del(&msg_ctx->daemon_out_list);
kfree(msg_ctx->msg);
msg_ctx->msg = NULL;
/* We do not expect a reply from the userspace daemon for any
* message type other than ECRYPTFS_MSG_REQUEST */
if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
out_unlock_msg_ctx:
mutex_unlock(&msg_ctx->mux);
out_unlock_daemon:
daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
mutex_unlock(&daemon->mux);
return rc;
}
/**
* 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)
{
struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
int rc;
if ((sizeof(*msg) + msg->data_len) != data_size) {
printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
"[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
(sizeof(*msg) + msg->data_len), data_size);
rc = -EINVAL;
goto out;
}
rc = ecryptfs_process_response(msg, euid, user_ns, pid, seq);
if (rc)
printk(KERN_ERR
"Error processing response message; rc = [%d]\n", rc);
out:
return rc;
}
/**
* ecryptfs_miscdev_write - handle write to daemon miscdev handle
* @file: File for misc dev handle (ignored)
* @buf: Buffer containing user data
* @count: Amount of data in @buf
* @ppos: Pointer to offset in file (ignored)
*
* miscdevfs packet format:
* Octet 0: Type
* Octets 1-4: network byte order msg_ctx->counter (0's for non-response)
* Octets 5-N0: Size of struct ecryptfs_message to follow
* Octets N0-N1: struct ecryptfs_message (including data)
*
* Returns the number of bytes read from @buf
*/
static ssize_t
ecryptfs_miscdev_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
__be32 counter_nbo;
u32 seq;
size_t packet_size, packet_size_length, i;
ssize_t sz = 0;
char *data;
uid_t euid = current_euid();
int rc;
if (count == 0)
goto out;
data = memdup_user(buf, count);
if (IS_ERR(data)) {
printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
__func__, PTR_ERR(data));
goto out;
}
sz = count;
i = 0;
switch (data[i++]) {
case ECRYPTFS_MSG_RESPONSE:
if (count < (1 + 4 + 1 + sizeof(struct ecryptfs_message))) {
printk(KERN_WARNING "%s: Minimum acceptable packet "
"size is [%zd], but amount of data written is "
"only [%zd]. Discarding response packet.\n",
__func__,
(1 + 4 + 1 + sizeof(struct ecryptfs_message)),
count);
goto out_free;
}
memcpy(&counter_nbo, &data[i], 4);
seq = be32_to_cpu(counter_nbo);
i += 4;
rc = ecryptfs_parse_packet_length(&data[i], &packet_size,
&packet_size_length);
if (rc) {
printk(KERN_WARNING "%s: Error parsing packet length; "
"rc = [%d]\n", __func__, rc);
goto out_free;
}
i += packet_size_length;
if ((1 + 4 + packet_size_length + packet_size) != count) {
printk(KERN_WARNING "%s: (1 + packet_size_length([%zd])"
" + packet_size([%zd]))([%zd]) != "
"count([%zd]). Invalid packet format.\n",
__func__, packet_size_length, packet_size,
(1 + packet_size_length + packet_size), count);
goto out_free;
}
rc = ecryptfs_miscdev_response(&data[i], packet_size,
euid, current_user_ns(),
task_pid(current), seq);
if (rc)
printk(KERN_WARNING "%s: Failed to deliver miscdev "
"response to requesting operation; rc = [%d]\n",
__func__, rc);
break;
case ECRYPTFS_MSG_HELO:
case ECRYPTFS_MSG_QUIT:
break;
default:
ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
"message of unrecognized type [%d]\n",
data[0]);
break;
}
out_free:
kfree(data);
out:
return sz;
}
static const struct file_operations ecryptfs_miscdev_fops = {
.open = ecryptfs_miscdev_open,
.poll = ecryptfs_miscdev_poll,
.read = ecryptfs_miscdev_read,
.write = ecryptfs_miscdev_write,
.release = ecryptfs_miscdev_release,
.llseek = noop_llseek,
};
static struct miscdevice ecryptfs_miscdev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "ecryptfs",
.fops = &ecryptfs_miscdev_fops
};
/**
* ecryptfs_init_ecryptfs_miscdev
*
* Messages sent to the userspace daemon from the kernel are placed on
* a queue associated with the daemon. The next read against the
* miscdev handle by that daemon will return the oldest message placed
* on the message queue for the daemon.
*
* Returns zero on success; non-zero otherwise
*/
int __init ecryptfs_init_ecryptfs_miscdev(void)
{
int rc;
atomic_set(&ecryptfs_num_miscdev_opens, 0);
rc = misc_register(&ecryptfs_miscdev);
if (rc)
printk(KERN_ERR "%s: Failed to register miscellaneous device "
"for communications with userspace daemons; rc = [%d]\n",
__func__, rc);
return rc;
}
/**
* ecryptfs_destroy_ecryptfs_miscdev
*
* All of the daemons must be exorcised prior to calling this
* function.
*/
void ecryptfs_destroy_ecryptfs_miscdev(void)
{
BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
misc_deregister(&ecryptfs_miscdev);
}
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