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Commit fbaa1227 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: audit: Simplify first-use allocation 



The first-use tty audit buffer allocation is a potential race
amongst multiple attempts at 'first-use'; only one 'winner' is
acceptable.

The successful buffer assignment occurs if tty_audit_buf == NULL
(which will also be the return from cmpxchg()); otherwise, another
racer 'won' and this buffer allocation is freed.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5493090f

drivers/tty/tty_audit.c

+7 −15
Original line number Diff line number Diff line
@@ -181,30 +181,22 @@ int tty_audit_push(void) 
 */

static struct tty_audit_buf *tty_audit_buf_get(void)

{

	struct tty_audit_buf *buf, *buf2;

	unsigned long flags;

	struct tty_audit_buf *buf;



	buf = current->signal->tty_audit_buf;

	if (buf)

		return buf;



	buf2 = tty_audit_buf_alloc();

	if (buf2 == NULL) {

	buf = tty_audit_buf_alloc();

	if (buf == NULL) {

		audit_log_lost("out of memory in TTY auditing");

		return NULL;

	}



	spin_lock_irqsave(&current->sighand->siglock, flags);

	buf = current->signal->tty_audit_buf;

	if (!buf) {

		current->signal->tty_audit_buf = buf2;

		buf = buf2;

		buf2 = NULL;

	}

	spin_unlock_irqrestore(&current->sighand->siglock, flags);

	if (buf2)

		tty_audit_buf_free(buf2);

	return buf;

	/* Race to use this buffer, free it if another wins */

	if (cmpxchg(&current->signal->tty_audit_buf, NULL, buf) != NULL)

		tty_audit_buf_free(buf);

	return current->signal->tty_audit_buf;

}



/**