tty: audit: Simplify first-use allocation (fbaa1227) · Commits · 戴 / test

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:

Peter Hurley <peter@hurleysoftware.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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;
		}

		/**

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