linux/security/keys/proc.c
David Howells 76d8aeabfe [PATCH] keys: Discard key spinlock and use RCU for key payload
The attached patch changes the key implementation in a number of ways:

 (1) It removes the spinlock from the key structure.

 (2) The key flags are now accessed using atomic bitops instead of
     write-locking the key spinlock and using C bitwise operators.

     The three instantiation flags are dealt with with the construction
     semaphore held during the request_key/instantiate/negate sequence, thus
     rendering the spinlock superfluous.

     The key flags are also now bit numbers not bit masks.

 (3) The key payload is now accessed using RCU. This permits the recursive
     keyring search algorithm to be simplified greatly since no locks need be
     taken other than the usual RCU preemption disablement. Searching now does
     not require any locks or semaphores to be held; merely that the starting
     keyring be pinned.

 (4) The keyring payload now includes an RCU head so that it can be disposed
     of by call_rcu(). This requires that the payload be copied on unlink to
     prevent introducing races in copy-down vs search-up.

 (5) The user key payload is now a structure with the data following it. It
     includes an RCU head like the keyring payload and for the same reason. It
     also contains a data length because the data length in the key may be
     changed on another CPU whilst an RCU protected read is in progress on the
     payload. This would then see the supposed RCU payload and the on-key data
     length getting out of sync.

     I'm tempted to drop the key's datalen entirely, except that it's used in
     conjunction with quota management and so is a little tricky to get rid
     of.

 (6) Update the keys documentation.

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-24 00:05:18 -07:00

257 lines
5.8 KiB
C

/* proc.c: proc files for key database enumeration
*
* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.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.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <asm/errno.h>
#include "internal.h"
#ifdef CONFIG_KEYS_DEBUG_PROC_KEYS
static int proc_keys_open(struct inode *inode, struct file *file);
static void *proc_keys_start(struct seq_file *p, loff_t *_pos);
static void *proc_keys_next(struct seq_file *p, void *v, loff_t *_pos);
static void proc_keys_stop(struct seq_file *p, void *v);
static int proc_keys_show(struct seq_file *m, void *v);
static struct seq_operations proc_keys_ops = {
.start = proc_keys_start,
.next = proc_keys_next,
.stop = proc_keys_stop,
.show = proc_keys_show,
};
static struct file_operations proc_keys_fops = {
.open = proc_keys_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
#endif
static int proc_key_users_open(struct inode *inode, struct file *file);
static void *proc_key_users_start(struct seq_file *p, loff_t *_pos);
static void *proc_key_users_next(struct seq_file *p, void *v, loff_t *_pos);
static void proc_key_users_stop(struct seq_file *p, void *v);
static int proc_key_users_show(struct seq_file *m, void *v);
static struct seq_operations proc_key_users_ops = {
.start = proc_key_users_start,
.next = proc_key_users_next,
.stop = proc_key_users_stop,
.show = proc_key_users_show,
};
static struct file_operations proc_key_users_fops = {
.open = proc_key_users_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
/*****************************************************************************/
/*
* declare the /proc files
*/
static int __init key_proc_init(void)
{
struct proc_dir_entry *p;
#ifdef CONFIG_KEYS_DEBUG_PROC_KEYS
p = create_proc_entry("keys", 0, NULL);
if (!p)
panic("Cannot create /proc/keys\n");
p->proc_fops = &proc_keys_fops;
#endif
p = create_proc_entry("key-users", 0, NULL);
if (!p)
panic("Cannot create /proc/key-users\n");
p->proc_fops = &proc_key_users_fops;
return 0;
} /* end key_proc_init() */
__initcall(key_proc_init);
/*****************************************************************************/
/*
* implement "/proc/keys" to provides a list of the keys on the system
*/
#ifdef CONFIG_KEYS_DEBUG_PROC_KEYS
static int proc_keys_open(struct inode *inode, struct file *file)
{
return seq_open(file, &proc_keys_ops);
}
static void *proc_keys_start(struct seq_file *p, loff_t *_pos)
{
struct rb_node *_p;
loff_t pos = *_pos;
spin_lock(&key_serial_lock);
_p = rb_first(&key_serial_tree);
while (pos > 0 && _p) {
pos--;
_p = rb_next(_p);
}
return _p;
}
static void *proc_keys_next(struct seq_file *p, void *v, loff_t *_pos)
{
(*_pos)++;
return rb_next((struct rb_node *) v);
}
static void proc_keys_stop(struct seq_file *p, void *v)
{
spin_unlock(&key_serial_lock);
}
static int proc_keys_show(struct seq_file *m, void *v)
{
struct rb_node *_p = v;
struct key *key = rb_entry(_p, struct key, serial_node);
struct timespec now;
unsigned long timo;
char xbuf[12];
now = current_kernel_time();
rcu_read_lock();
/* come up with a suitable timeout value */
if (key->expiry == 0) {
memcpy(xbuf, "perm", 5);
}
else if (now.tv_sec >= key->expiry) {
memcpy(xbuf, "expd", 5);
}
else {
timo = key->expiry - now.tv_sec;
if (timo < 60)
sprintf(xbuf, "%lus", timo);
else if (timo < 60*60)
sprintf(xbuf, "%lum", timo / 60);
else if (timo < 60*60*24)
sprintf(xbuf, "%luh", timo / (60*60));
else if (timo < 60*60*24*7)
sprintf(xbuf, "%lud", timo / (60*60*24));
else
sprintf(xbuf, "%luw", timo / (60*60*24*7));
}
#define showflag(KEY, LETTER, FLAG) \
(test_bit(FLAG, &(KEY)->flags) ? LETTER : '-')
seq_printf(m, "%08x %c%c%c%c%c%c %5d %4s %06x %5d %5d %-9.9s ",
key->serial,
showflag(key, 'I', KEY_FLAG_INSTANTIATED),
showflag(key, 'R', KEY_FLAG_REVOKED),
showflag(key, 'D', KEY_FLAG_DEAD),
showflag(key, 'Q', KEY_FLAG_IN_QUOTA),
showflag(key, 'U', KEY_FLAG_USER_CONSTRUCT),
showflag(key, 'N', KEY_FLAG_NEGATIVE),
atomic_read(&key->usage),
xbuf,
key->perm,
key->uid,
key->gid,
key->type->name);
#undef showflag
if (key->type->describe)
key->type->describe(key, m);
seq_putc(m, '\n');
rcu_read_unlock();
return 0;
}
#endif /* CONFIG_KEYS_DEBUG_PROC_KEYS */
/*****************************************************************************/
/*
* implement "/proc/key-users" to provides a list of the key users
*/
static int proc_key_users_open(struct inode *inode, struct file *file)
{
return seq_open(file, &proc_key_users_ops);
}
static void *proc_key_users_start(struct seq_file *p, loff_t *_pos)
{
struct rb_node *_p;
loff_t pos = *_pos;
spin_lock(&key_user_lock);
_p = rb_first(&key_user_tree);
while (pos > 0 && _p) {
pos--;
_p = rb_next(_p);
}
return _p;
}
static void *proc_key_users_next(struct seq_file *p, void *v, loff_t *_pos)
{
(*_pos)++;
return rb_next((struct rb_node *) v);
}
static void proc_key_users_stop(struct seq_file *p, void *v)
{
spin_unlock(&key_user_lock);
}
static int proc_key_users_show(struct seq_file *m, void *v)
{
struct rb_node *_p = v;
struct key_user *user = rb_entry(_p, struct key_user, node);
seq_printf(m, "%5u: %5d %d/%d %d/%d %d/%d\n",
user->uid,
atomic_read(&user->usage),
atomic_read(&user->nkeys),
atomic_read(&user->nikeys),
user->qnkeys,
KEYQUOTA_MAX_KEYS,
user->qnbytes,
KEYQUOTA_MAX_BYTES
);
return 0;
}