Patch "serial: max3100: Lock port->lock when calling uart_handle_cts_change()" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     serial-max3100-lock-port-lock-when-calling-uart_hand.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 6f6565f9e888492dd01eb8f941e3c94623dc56b1
Author: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Date:   Tue Apr 2 22:50:28 2024 +0300

    serial: max3100: Lock port->lock when calling uart_handle_cts_change()
    
    [ Upstream commit 77ab53371a2066fdf9b895246505f5ef5a4b5d47 ]
    
    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@xxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20240402195306.269276-2-andriy.shevchenko@xxxxxxxxxxxxxxx
    Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c
index 371569a0fd00a..915d7753eec2f 100644
--- 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 ch, flg, status = 0;
 	int ret = 0, cts;
@@ -253,6 +253,17 @@ 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);