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serdev: ttyport: add missing receive_buf sanity checks

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The receive_buf tty-port callback should return the number of bytes
accepted and must specifically never return a negative errno (or a value
larger than the buffer size) to the tty layer.

A serdev driver not providing a receive_buf callback would currently
cause the flush_to_ldisc() worker to spin in a tight loop when the tty
buffer pointers are incremented with -EINVAL (-22) after data has been
received.

A serdev driver occasionally returning a negative errno (or a too large
byte count) could cause information leaks or crashes when accessing
memory outside the tty buffers in consecutive callbacks.

Fixes: cd6484e183 ("serdev: Introduce new bus for serial attached devices")
Cc: stable <stable@vger.kernel.org>	# 4.11
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2017-11-03 15:30:52 +01:00 committed by Greg Kroah-Hartman
parent 0ff3ab7019
commit eb28168362
1 changed files with 12 additions and 1 deletions
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13
drivers/tty/serdev/serdev-ttyport.c
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@ -27,11 +27,22 @@ static int ttyport_receive_buf(struct tty_port *port, const unsigned char *cp,
{
struct serdev_controller *ctrl = port->client_data;
struct serport *serport = serdev_controller_get_drvdata(ctrl);
int ret;
if (!test_bit(SERPORT_ACTIVE, &serport->flags))
return 0;
return serdev_controller_receive_buf(ctrl, cp, count);
ret = serdev_controller_receive_buf(ctrl, cp, count);
dev_WARN_ONCE(&ctrl->dev, ret < 0 || ret > count,
"receive_buf returns %d (count = %zu)\n",
ret, count);
if (ret < 0)
return 0;
else if (ret > count)
return count;
return ret;
}
static void ttyport_write_wakeup(struct tty_port *port)