Commit 7098296a authored Sep 17, 2015 by Dmitry Vyukov Committed by Greg Kroah-Hartman Oct 04, 2015

tty: fix data race in flush_to_ldisc



flush_to_ldisc reads port->itty and checks that it is not NULL,
concurrently release_tty sets port->itty to NULL. It is possible
that flush_to_ldisc loads port->itty once, ensures that it is
not NULL, but then reloads it again and uses. The second load
can already return NULL, which will cause a crash.

Use READ_ONCE to read port->itty.

The data race was found with KernelThreadSanitizer (KTSAN).

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent e81107d4

drivers/tty/tty_buffer.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -467,7 +467,7 @@ static void flush_to_ldisc(struct work_struct *work)
		struct tty_struct *tty;
		struct tty_ldisc *disc;

		tty = port->itty;
		tty = READ_ONCE(port->itty);
		if (tty == NULL)
		return;