From 98d031aeff6d4a4c2897d75cdb0a7701deb90f04 Mon Sep 17 00:00:00 2001 From: Erwan Le Ray Date: Thu, 4 Mar 2021 17:23:02 +0100 Subject: [PATCH] serial: stm32: fix a deadlock in set_termios BugLink: https://bugs.launchpad.net/bugs/1929455 [ Upstream commit 436c97936001776f16153771ee887f125443e974 ] CTS/RTS GPIOs support that has been added recently to STM32 UART driver has introduced scheduled code in a set_termios part protected by a spin lock. This generates a potential deadlock scenario: Chain exists of: &irq_desc_lock_class --> console_owner --> &port_lock_key Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&port_lock_key); lock(console_owner); lock(&port_lock_key); lock(&irq_desc_lock_class); *** DEADLOCK *** 4 locks held by stty/766: Move the scheduled code after the spinlock. Fixes: 6cf61b9bd7cc ("tty: serial: Add modem control gpio support for STM32 UART") Signed-off-by: Erwan Le Ray Link: https://lore.kernel.org/r/20210304162308.8984-8-erwan.leray@foss.st.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin Signed-off-by: Kamal Mostafa Signed-off-by: Kelsey Skunberg --- drivers/tty/serial/stm32-usart.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index 85e9a4d4e91d..44522ddc7e6d 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -827,12 +827,6 @@ static void stm32_usart_set_termios(struct uart_port *port, cr3 |= USART_CR3_CTSE | USART_CR3_RTSE; } - /* Handle modem control interrupts */ - if (UART_ENABLE_MS(port, termios->c_cflag)) - stm32_usart_enable_ms(port); - else - stm32_usart_disable_ms(port); - usartdiv = DIV_ROUND_CLOSEST(port->uartclk, baud); /* @@ -914,6 +908,12 @@ static void stm32_usart_set_termios(struct uart_port *port, stm32_usart_set_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit)); spin_unlock_irqrestore(&port->lock, flags); + + /* Handle modem control interrupts */ + if (UART_ENABLE_MS(port, termios->c_cflag)) + stm32_usart_enable_ms(port); + else + stm32_usart_disable_ms(port); } static const char *stm32_usart_type(struct uart_port *port) -- 2.39.5