tree d5faab1ed808c7fc3d55be88d431452b43e1e63e
parent e81107d4c6bd098878af9796b24edc8d4a9524fd
author Dmitry Vyukov <dvyukov@google.com> 1442503028 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1443981820 +0100

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>