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authorDavid Howells <dhowells@redhat.com>2006-04-10 22:54:26 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-04-11 06:18:45 -0700
commit1a26feb9622f1b1bc5e4f5f60f65557b73c38cbf (patch)
tree2404fc0d346127b71b9c30d9f9c95603c652ac93 /security/keys
parent25a80759c5c237f0ecf57eb11fdd4efb21079c88 (diff)
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[PATCH] Keys: Improve usage of memory barriers and remove IRQ disablement
Remove an unnecessary memory barrier (implicit in rcu_dereference()) from install_session_keyring(). install_session_keyring() is also rearranged a little to make it slightly more efficient. As install_*_keyring() may schedule (in synchronize_rcu() or keyring_alloc()), they may not be entered with interrupts disabled - and so there's no point saving the interrupt disablement state over the critical section. exec_keys() will also be invoked with interrupts enabled, and so that doesn't need to save the interrupt state either. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'security/keys')
-rw-r--r--security/keys/process_keys.c41
1 files changed, 20 insertions, 21 deletions
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index f6940618e34..217a0bef3c8 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -168,11 +168,12 @@ error:
*/
int install_process_keyring(struct task_struct *tsk)
{
- unsigned long flags;
struct key *keyring;
char buf[20];
int ret;
+ might_sleep();
+
if (!tsk->signal->process_keyring) {
sprintf(buf, "_pid.%u", tsk->tgid);
@@ -183,12 +184,12 @@ int install_process_keyring(struct task_struct *tsk)
}
/* attach keyring */
- spin_lock_irqsave(&tsk->sighand->siglock, flags);
+ spin_lock_irq(&tsk->sighand->siglock);
if (!tsk->signal->process_keyring) {
tsk->signal->process_keyring = keyring;
keyring = NULL;
}
- spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
+ spin_unlock_irq(&tsk->sighand->siglock);
key_put(keyring);
}
@@ -207,38 +208,37 @@ error:
static int install_session_keyring(struct task_struct *tsk,
struct key *keyring)
{
- unsigned long flags;
struct key *old;
char buf[20];
- int ret;
+
+ might_sleep();
/* create an empty session keyring */
if (!keyring) {
sprintf(buf, "_ses.%u", tsk->tgid);
keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
- if (IS_ERR(keyring)) {
- ret = PTR_ERR(keyring);
- goto error;
- }
+ if (IS_ERR(keyring))
+ return PTR_ERR(keyring);
}
else {
atomic_inc(&keyring->usage);
}
/* install the keyring */
- spin_lock_irqsave(&tsk->sighand->siglock, flags);
- old = rcu_dereference(tsk->signal->session_keyring);
+ spin_lock_irq(&tsk->sighand->siglock);
+ old = tsk->signal->session_keyring;
rcu_assign_pointer(tsk->signal->session_keyring, keyring);
- spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
+ spin_unlock_irq(&tsk->sighand->siglock);
- ret = 0;
+ /* we're using RCU on the pointer, but there's no point synchronising
+ * on it if it didn't previously point to anything */
+ if (old) {
+ synchronize_rcu();
+ key_put(old);
+ }
- /* we're using RCU on the pointer */
- synchronize_rcu();
- key_put(old);
-error:
- return ret;
+ return 0;
} /* end install_session_keyring() */
@@ -311,7 +311,6 @@ void exit_keys(struct task_struct *tsk)
*/
int exec_keys(struct task_struct *tsk)
{
- unsigned long flags;
struct key *old;
/* newly exec'd tasks don't get a thread keyring */
@@ -323,10 +322,10 @@ int exec_keys(struct task_struct *tsk)
key_put(old);
/* discard the process keyring from a newly exec'd task */
- spin_lock_irqsave(&tsk->sighand->siglock, flags);
+ spin_lock_irq(&tsk->sighand->siglock);
old = tsk->signal->process_keyring;
tsk->signal->process_keyring = NULL;
- spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
+ spin_unlock_irq(&tsk->sighand->siglock);
key_put(old);