AUDIT: Fix livelock in audit_serial().

 * (timestamp,serial) tuple is unique for each syscall and is live from

 * (timestamp,serial) tuple is unique for each syscall and is live from

 * syscall entry to syscall exit.

 * syscall entry to syscall exit.

 *

 *

 * Atomic values are only guaranteed to be 24-bit, so we count down.

 *

 * NOTE: Another possibility is to store the formatted records off the

 * NOTE: Another possibility is to store the formatted records off the

 * audit context (for those records that have a context), and emit them

 * audit context (for those records that have a context), and emit them

 * all at syscall exit.  However, this could delay the reporting of

 * all at syscall exit.  However, this could delay the reporting of

 * significant errors until syscall exit (or never, if the system

 * significant errors until syscall exit (or never, if the system

 * halts). */

 * halts). */

unsigned int audit_serial(void)

unsigned int audit_serial(void)

{

{

	static atomic_t serial = ATOMIC_INIT(0xffffff);

	static spinlock_t serial_lock = SPIN_LOCK_UNLOCKED;

	unsigned int a, b;

	static unsigned int serial = 0;

	unsigned long flags;

	unsigned int ret;

	do {

	spin_lock_irqsave(&serial_lock, flags);

		a = atomic_read(&serial);

	ret = serial++;

		if (atomic_dec_and_test(&serial))

	spin_unlock_irqrestore(&serial_lock, flags);

			atomic_set(&serial, 0xffffff);

		b = atomic_read(&serial);

	} while (b != a - 1);

	return 0xffffff - b;

	return ret;

}

}

static inline void audit_get_stamp(struct audit_context *ctx, 

static inline void audit_get_stamp(struct audit_context *ctx,