From: Johan Hovold johan@kernel.org
commit 00de977f9e0aa9760d9a79d1e41ff780f74e3424 upstream.
Commit 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close") converted serial core to use tty_port_close() but failed to notice that the transmit buffer still needs to be freed on final close.
Not freeing the transmit buffer means that the buffer is no longer cleared on next open so that any ioctl() waiting for the buffer to drain might wait indefinitely (e.g. on termios changes) or that stale data can end up being transmitted in case tx is restarted.
Furthermore, the buffer of any port that has been opened would leak on driver unbind.
Note that the port lock is held when clearing the buffer pointer due to the ldisc race worked around by commit a5ba1d95e46e ("uart: fix race between uart_put_char() and uart_shutdown()").
Also note that the tty-port shutdown() callback is not called for console ports so it is not strictly necessary to free the buffer page after releasing the lock (cf. d72402145ace ("tty/serial: do not free trasnmit buffer page under port lock")).
Link: https://lore.kernel.org/r/319321886d97c456203d5c6a576a5480d07c3478.163578168... Fixes: 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close") Cc: stable@vger.kernel.org # 4.9 Cc: Rob Herring robh@kernel.org Reported-by: Baruch Siach baruch@tkos.co.il Tested-by: Baruch Siach baruch@tkos.co.il Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20211108085431.12637-1-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/serial_core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
--- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1522,6 +1522,7 @@ static void uart_tty_port_shutdown(struc { struct uart_state *state = container_of(port, struct uart_state, port); struct uart_port *uport = uart_port_check(state); + char *buf;
/* * At this point, we stop accepting input. To do this, we @@ -1543,8 +1544,18 @@ static void uart_tty_port_shutdown(struc */ tty_port_set_suspended(port, 0);
- uart_change_pm(state, UART_PM_STATE_OFF); + /* + * Free the transmit buffer. + */ + spin_lock_irq(&uport->lock); + buf = state->xmit.buf; + state->xmit.buf = NULL; + spin_unlock_irq(&uport->lock); + + if (buf) + free_page((unsigned long)buf);
+ uart_change_pm(state, UART_PM_STATE_OFF); }
static void uart_wait_until_sent(struct tty_struct *tty, int timeout)