[PATCH 5.19 0920/1157] serial: 8250_dw: Take port lock while accessing LSR

Greg Kroah-Hartman
2022-08-16T00:42:56Z

From: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

[ Upstream commit b9491b2e45d71eb64245560e208897af95ffbf95 ]

Accessing LSR requires port lock because it mutates lsr_saved_flags
in serial_lsr_in().

Fixes: 197eb5c416ff ("serial: 8250_dw: Use serial_lsr_in() in dw8250_handle_irq()")
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/c5879db7-bee9-93f-526e-872a292442@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/8250/8250_dw.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index c0ab67033a25..d0dfbf1fc9d8 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -266,7 +266,10 @@ static int dw8250_handle_irq(struct uart_port *p)

/* Manually stop the Rx DMA transfer when acting as flow controller */
if (quirks & DW_UART_QUIRK_IS_DMA_FC && up->dma && up->dma->rx_running && rx_timeout) {
+ spin_lock_irqsave(&p->lock, flags);
status = serial_lsr_in(up);
+ spin_unlock_irqrestore(&p->lock, flags);
+
if (status & (UART_LSR_DR | UART_LSR_BI)) {
dw8250_writel_ext(p, RZN1_UART_RDMACR, 0);
dw8250_writel_ext(p, DW_UART_DMASA, 1);
--
2.35.1