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| author | Peter Hurley <peter@hurleysoftware.com> | 2015-07-12 21:05:26 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-07-23 18:08:28 -0700 |
| commit | e144c58cad6667876173dd76977e9e6557e34941 (patch) | |
| tree | 77a8fb4466d880c78ccc913fa29e69fc3aac0f5f | |
| parent | 7525a9901b5ee3c84933ad069e41506c37404ddc (diff) | |
| download | linux-stable-e144c58cad6667876173dd76977e9e6557e34941.tar.gz linux-stable-e144c58cad6667876173dd76977e9e6557e34941.tar.bz2 linux-stable-e144c58cad6667876173dd76977e9e6557e34941.zip | |
serial: core: Fix crashes while echoing when closing
While closing, new rx data may be received after the input buffers
have been flushed but before stop_rx() halts receiving [1]. The
new data might not be processed by flush_to_ldisc() until after
uart_shutdown() and normal input processing is re-enabled (ie.,
tty->closing = 0). The race is outlined below:
CPU 0 | CPU 1
|
uart_close() |
tty_port_close_start() |
tty->closing = 1 |
tty_ldisc_flush() |
| => IRQ
| while (LSR & data ready)
| uart_insert_char()
| tty_flip_buffer_push()
| <= EOI
stop_rx() | .
uart_shutdown() | .
free xmit.buf | .
tty_port_tty_set(NULL) | .
tty->closing = 0 | .
| flush_to_ldisc()
| n_tty_receive_buf_common()
| __receive_buf()
| ...
| commit_echoes()
| uart_flush_chars()
| __uart_start()
| ** OOPS on port.tty deref **
tty_ldisc_flush() |
Input processing must be prevented from echoing (tty->closing = 1)
until _after_ the input buffers have been flushed again at the end
of uart_close().
[1] In fact, some input may actually be buffered _after_ stop_rx()
since the rx interrupt may have already triggered but not yet been
handled when stop_rx() disables rx interrupts.
Fixes: 2e758910832d ("serial: core: Flush ldisc after dropping port
mutex in uart_close()")
Reported-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 7ae1592f7ec9..f36852067f20 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1418,7 +1418,7 @@ static void uart_close(struct tty_struct *tty, struct file *filp) mutex_lock(&port->mutex); uart_shutdown(tty, state); tty_port_tty_set(port, NULL); - tty->closing = 0; + spin_lock_irqsave(&port->lock, flags); if (port->blocked_open) { @@ -1444,6 +1444,7 @@ static void uart_close(struct tty_struct *tty, struct file *filp) mutex_unlock(&port->mutex); tty_ldisc_flush(tty); + tty->closing = 0; } static void uart_wait_until_sent(struct tty_struct *tty, int timeout) |