On Fri, Jan 18, 2019 at 04:56:04PM +0800, Li RongQing wrote:
> There still is a race window after the commit b027e2298bd588
> ("tty: fix data race between tty_init_dev and flush of buf"),
> and we encountered this crash issue if receive_buf call comes
> before tty initialization completes in n_tty_open and
> tty->driver_data may be NULL.
>
> CPU0 CPU1
> ---- ----
> n_tty_open
> tty_init_dev
> tty_ldisc_unlock
> schedule
> flush_to_ldisc
> receive_buf
> tty_port_default_receive_buf
> tty_ldisc_receive_buf
> n_tty_receive_buf_common
> __receive_buf
> uart_flush_chars
> uart_start
> /*tty->driver_data is NULL*/
> tty->ops->open
> /*init tty->driver_data*/
>
> it can be fixed by extending ldisc semaphore lock in tty_init_dev
> to driver_data initialized completely after tty->ops->open(), but
> this will lead to put lock on one function and unlock in some other
> function, and hard to maintain, so fix this race only by checking
> tty->driver_data when receiving, and return if tty->driver_data
> is NULL
>
> Signed-off-by: Wang Li <[email protected]>
> Signed-off-by: Zhang Yu <[email protected]>
> Signed-off-by: Li RongQing <[email protected]>
> ---
> drivers/tty/tty_port.c | 3 +++
> 1 file changed, 3 insertions(+)
What changed in this version, from the other versions? That is always
to be listed below the --- line, as the documentation states.
Please fix up and do a v4 with all of this information.
thanks,
greg k-h
