2009-09-02 02:14:00 -06:00
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/* Key garbage collector
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*
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* Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#include <linux/module.h>
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#include <keys/keyring-type.h>
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#include "internal.h"
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/*
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* Delay between key revocation/expiry in seconds
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*/
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unsigned key_gc_delay = 5 * 60;
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/*
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* Reaper
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*/
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static void key_gc_timer_func(unsigned long);
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static void key_garbage_collector(struct work_struct *);
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static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0);
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static DECLARE_WORK(key_gc_work, key_garbage_collector);
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static key_serial_t key_gc_cursor; /* the last key the gc considered */
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2009-09-14 10:26:13 -06:00
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static bool key_gc_again;
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2009-09-02 02:14:00 -06:00
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static unsigned long key_gc_executing;
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static time_t key_gc_next_run = LONG_MAX;
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2009-09-14 10:26:13 -06:00
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static time_t key_gc_new_timer;
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2009-09-02 02:14:00 -06:00
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/*
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* Schedule a garbage collection run
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* - precision isn't particularly important
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*/
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void key_schedule_gc(time_t gc_at)
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{
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unsigned long expires;
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time_t now = current_kernel_time().tv_sec;
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kenter("%ld", gc_at - now);
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2009-09-14 10:26:13 -06:00
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if (gc_at <= now) {
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2009-09-02 02:14:00 -06:00
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schedule_work(&key_gc_work);
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} else if (gc_at < key_gc_next_run) {
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expires = jiffies + (gc_at - now) * HZ;
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mod_timer(&key_gc_timer, expires);
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}
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}
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/*
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* The garbage collector timer kicked off
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*/
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static void key_gc_timer_func(unsigned long data)
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{
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kenter("");
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key_gc_next_run = LONG_MAX;
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schedule_work(&key_gc_work);
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}
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/*
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* Garbage collect pointers from a keyring
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* - return true if we altered the keyring
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*/
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static bool key_gc_keyring(struct key *keyring, time_t limit)
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KEYS: Add a keyctl to install a process's session keyring on its parent [try #6]
Add a keyctl to install a process's session keyring onto its parent. This
replaces the parent's session keyring. Because the COW credential code does
not permit one process to change another process's credentials directly, the
change is deferred until userspace next starts executing again. Normally this
will be after a wait*() syscall.
To support this, three new security hooks have been provided:
cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in
the blank security creds and key_session_to_parent() - which asks the LSM if
the process may replace its parent's session keyring.
The replacement may only happen if the process has the same ownership details
as its parent, and the process has LINK permission on the session keyring, and
the session keyring is owned by the process, and the LSM permits it.
Note that this requires alteration to each architecture's notify_resume path.
This has been done for all arches barring blackfin, m68k* and xtensa, all of
which need assembly alteration to support TIF_NOTIFY_RESUME. This allows the
replacement to be performed at the point the parent process resumes userspace
execution.
This allows the userspace AFS pioctl emulation to fully emulate newpag() and
the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to
alter the parent process's PAG membership. However, since kAFS doesn't use
PAGs per se, but rather dumps the keys into the session keyring, the session
keyring of the parent must be replaced if, for example, VIOCSETTOK is passed
the newpag flag.
This can be tested with the following program:
#include <stdio.h>
#include <stdlib.h>
#include <keyutils.h>
#define KEYCTL_SESSION_TO_PARENT 18
#define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0)
int main(int argc, char **argv)
{
key_serial_t keyring, key;
long ret;
keyring = keyctl_join_session_keyring(argv[1]);
OSERROR(keyring, "keyctl_join_session_keyring");
key = add_key("user", "a", "b", 1, keyring);
OSERROR(key, "add_key");
ret = keyctl(KEYCTL_SESSION_TO_PARENT);
OSERROR(ret, "KEYCTL_SESSION_TO_PARENT");
return 0;
}
Compiled and linked with -lkeyutils, you should see something like:
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: _ses
355907932 --alswrv 4043 -1 \_ keyring: _uid.4043
[dhowells@andromeda ~]$ /tmp/newpag
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: _ses
1055658746 --alswrv 4043 4043 \_ user: a
[dhowells@andromeda ~]$ /tmp/newpag hello
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: hello
340417692 --alswrv 4043 4043 \_ user: a
Where the test program creates a new session keyring, sticks a user key named
'a' into it and then installs it on its parent.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
2009-09-02 02:14:21 -06:00
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__releases(key_serial_lock)
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2009-09-02 02:14:00 -06:00
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{
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struct keyring_list *klist;
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struct key *key;
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int loop;
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kenter("%x", key_serial(keyring));
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if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
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goto dont_gc;
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/* scan the keyring looking for dead keys */
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klist = rcu_dereference(keyring->payload.subscriptions);
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if (!klist)
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goto dont_gc;
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for (loop = klist->nkeys - 1; loop >= 0; loop--) {
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key = klist->keys[loop];
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if (test_bit(KEY_FLAG_DEAD, &key->flags) ||
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(key->expiry > 0 && key->expiry <= limit))
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goto do_gc;
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}
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dont_gc:
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kleave(" = false");
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return false;
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do_gc:
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key_gc_cursor = keyring->serial;
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key_get(keyring);
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spin_unlock(&key_serial_lock);
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keyring_gc(keyring, limit);
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key_put(keyring);
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kleave(" = true");
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return true;
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}
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/*
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* Garbage collector for keys
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* - this involves scanning the keyrings for dead, expired and revoked keys
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* that have overstayed their welcome
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*/
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static void key_garbage_collector(struct work_struct *work)
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{
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struct rb_node *rb;
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key_serial_t cursor;
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struct key *key, *xkey;
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2009-09-14 10:26:13 -06:00
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time_t new_timer = LONG_MAX, limit, now;
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2009-09-02 02:14:00 -06:00
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2009-09-14 10:26:13 -06:00
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now = current_kernel_time().tv_sec;
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kenter("[%x,%ld]", key_gc_cursor, key_gc_new_timer - now);
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2009-09-02 02:14:00 -06:00
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if (test_and_set_bit(0, &key_gc_executing)) {
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2009-09-14 10:26:13 -06:00
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key_schedule_gc(current_kernel_time().tv_sec + 1);
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kleave(" [busy; deferring]");
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2009-09-02 02:14:00 -06:00
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return;
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}
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2009-09-14 10:26:13 -06:00
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limit = now;
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2009-09-02 02:14:00 -06:00
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if (limit > key_gc_delay)
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limit -= key_gc_delay;
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else
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limit = key_gc_delay;
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spin_lock(&key_serial_lock);
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2009-09-14 10:26:13 -06:00
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if (unlikely(RB_EMPTY_ROOT(&key_serial_tree))) {
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spin_unlock(&key_serial_lock);
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clear_bit(0, &key_gc_executing);
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return;
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}
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2009-09-02 02:14:00 -06:00
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cursor = key_gc_cursor;
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if (cursor < 0)
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cursor = 0;
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2009-09-14 10:26:13 -06:00
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if (cursor > 0)
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new_timer = key_gc_new_timer;
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else
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key_gc_again = false;
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2009-09-02 02:14:00 -06:00
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/* find the first key above the cursor */
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key = NULL;
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rb = key_serial_tree.rb_node;
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while (rb) {
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xkey = rb_entry(rb, struct key, serial_node);
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if (cursor < xkey->serial) {
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key = xkey;
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rb = rb->rb_left;
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} else if (cursor > xkey->serial) {
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rb = rb->rb_right;
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} else {
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rb = rb_next(rb);
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if (!rb)
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goto reached_the_end;
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key = rb_entry(rb, struct key, serial_node);
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break;
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}
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}
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if (!key)
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goto reached_the_end;
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/* trawl through the keys looking for keyrings */
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for (;;) {
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2009-09-14 10:26:13 -06:00
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if (key->expiry > now && key->expiry < new_timer) {
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kdebug("will expire %x in %ld",
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key_serial(key), key->expiry - now);
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2009-09-02 02:14:00 -06:00
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new_timer = key->expiry;
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2009-09-14 10:26:13 -06:00
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}
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2009-09-02 02:14:00 -06:00
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if (key->type == &key_type_keyring &&
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2009-09-14 10:26:13 -06:00
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key_gc_keyring(key, limit))
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/* the gc had to release our lock so that the keyring
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* could be modified, so we have to get it again */
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goto gc_released_our_lock;
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2009-09-02 02:14:00 -06:00
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rb = rb_next(&key->serial_node);
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2009-09-14 10:26:13 -06:00
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if (!rb)
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goto reached_the_end;
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2009-09-02 02:14:00 -06:00
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key = rb_entry(rb, struct key, serial_node);
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}
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2009-09-14 10:26:13 -06:00
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gc_released_our_lock:
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kdebug("gc_released_our_lock");
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key_gc_new_timer = new_timer;
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key_gc_again = true;
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2009-09-02 02:14:00 -06:00
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clear_bit(0, &key_gc_executing);
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2009-09-14 10:26:13 -06:00
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schedule_work(&key_gc_work);
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kleave(" [continue]");
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2009-09-02 02:14:00 -06:00
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return;
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2009-09-14 10:26:13 -06:00
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/* when we reach the end of the run, we set the timer for the next one */
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2009-09-02 02:14:00 -06:00
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reached_the_end:
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2009-09-14 10:26:13 -06:00
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kdebug("reached_the_end");
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spin_unlock(&key_serial_lock);
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key_gc_new_timer = new_timer;
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2009-09-02 02:14:00 -06:00
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key_gc_cursor = 0;
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2009-09-14 10:26:13 -06:00
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clear_bit(0, &key_gc_executing);
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if (key_gc_again) {
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/* there may have been a key that expired whilst we were
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* scanning, so if we discarded any links we should do another
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* scan */
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new_timer = now + 1;
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key_schedule_gc(new_timer);
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} else if (new_timer < LONG_MAX) {
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new_timer += key_gc_delay;
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key_schedule_gc(new_timer);
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}
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kleave(" [end]");
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2009-09-02 02:14:00 -06:00
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}
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