serial: max3100: Lock port->lock when calling uart_handle_cts_change()

uart_handle_cts_change() has to be called with port lock taken,
Since we run it in a separate work, the lock may not be taken at
the time of running. Make sure that it's taken by explicitly doing
that. Without it we got a splat:

  WARNING: CPU: 0 PID: 10 at drivers/tty/serial/serial_core.c:3491 uart_handle_cts_change+0xa6/0xb0
  ...
  Workqueue: max3100-0 max3100_work [max3100]
  RIP: 0010:uart_handle_cts_change+0xa6/0xb0
  ...
   max3100_handlerx+0xc5/0x110 [max3100]
   max3100_work+0x12a/0x340 [max3100]

Fixes: 7831d56b0a35 ("tty: MAX3100")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240402195306.269276-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c
index b83eee37c17d4f51fb302ee76dd3c9146db94dbe..53dde3391abf494112eee9b7c3f019d4b16a6a4d 100644 (file)
--- a/drivers/tty/serial/max3100.c
+++ b/drivers/tty/serial/max3100.c
@@ -213,7 +213,7 @@ static int max3100_sr(struct max3100_port *s, u16 tx, u16 *rx)
        return 0;
 }
 
-static int max3100_handlerx(struct max3100_port *s, u16 rx)
+static int max3100_handlerx_unlocked(struct max3100_port *s, u16 rx)
 {
        unsigned int status = 0;
        int ret = 0, cts;
@@ -254,6 +254,17 @@ static int max3100_handlerx(struct max3100_port *s, u16 rx)
        return ret;
 }
 
+static int max3100_handlerx(struct max3100_port *s, u16 rx)
+{
+       unsigned long flags;
+       int ret;
+
+       uart_port_lock_irqsave(&s->port, &flags);
+       ret = max3100_handlerx_unlocked(s, rx);
+       uart_port_unlock_irqrestore(&s->port, flags);
+       return ret;
+}
+
 static void max3100_work(struct work_struct *w)
 {
        struct max3100_port *s = container_of(w, struct max3100_port, work);