receive_room is used to control the amount of data the flip
buffer work can push to the read buffer. This update is unsafe:
CPU 0 | CPU 1
|
| n_tty_read()
| n_tty_set_room()
| left = <calc of space>
n_tty_receive_buf() |
<push data to buffer> |
n_tty_set_room() |
left = <calc of space> |
tty->receive_room = left |
| tty->receive_room = left
receive_room is now updated with a stale calculation of the
available buffer space, and the subsequent work loop will likely
overwrite unread data in the input buffer.
Update receive_room atomically with the calculation of the
available buffer space.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
b848305276