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Subject[PATCH] drivers/tty/serial: extern function which for release resource, need check pointer, before free it

for extern function uart_remove_one_port:
need check pointer whether be NULL, before the main work.
just like what the other extern function uart_add_one_port has done.
uart_add_one_port and uart_remove_one_port are pair

information:
for the callers (such as drivers/tty/serial/jsm: jsm_tty.c, jsm_driver.c)
they realy assume that:
they still can call uart_remove_one_port, after uart_add_one_port failed
we (as an extern function), have to understand it (just like kfree).


Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
drivers/tty/serial/serial_core.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 2c7230a..bd65549 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2642,6 +2642,7 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
{
struct uart_state *state = drv->state + uport->line;
struct tty_port *port = &state->port;
+ int ret = 0;

BUG_ON(in_interrupt());

@@ -2656,6 +2657,11 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
* succeeding while we shut down the port.
*/
mutex_lock(&port->mutex);
+ if (!state->uart_port) {
+ mutex_unlock(&port->mutex);
+ ret = -EINVAL;
+ goto out;
+ }
uport->flags |= UPF_DEAD;
mutex_unlock(&port->mutex);

@@ -2679,9 +2685,10 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
uport->type = PORT_UNKNOWN;

state->uart_port = NULL;
+out:
mutex_unlock(&port_mutex);

- return 0;
+ return ret;
}

/*
--
1.7.10.4

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