Merge tag 'tty-6.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial driver fixes from Greg KH:
 "Here are some small serial and vt fixes. These include:

   - 8250 driver fixes relating to dma issues

   - stm32 serial driver fix for threaded irqs

   - vc_screen bugfix for reported problems.

  All have been in linux-next for a while with no reported problems"

* tag 'tty-6.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF
  serial: 8250_dma: Fix DMA Rx rearm race
  serial: 8250_dma: Fix DMA Rx completion race
  serial: stm32: Merge hard IRQ and threaded IRQ handling into single IRQ handler

3 files changed, 27 insertions, 36 deletions

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 37d6af2ec427..7fa66501792d 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -43,15 +43,23 @@ static void __dma_rx_complete(struct uart_8250_port *p)
 	struct uart_8250_dma	*dma = p->dma;
 	struct tty_port		*tty_port = &p->port.state->port;
 	struct dma_tx_state	state;
+	enum dma_status		dma_status;
 	int			count;
 
-	dma->rx_running = 0;
-	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
+	/*
+	 * New DMA Rx can be started during the completion handler before it
+	 * could acquire port's lock and it might still be ongoing. Don't to
+	 * anything in such case.
+	 */
+	dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
+	if (dma_status == DMA_IN_PROGRESS)
+		return;
 
 	count = dma->rx_size - state.residue;
 
 	tty_insert_flip_string(tty_port, dma->rx_buf, count);
 	p->port.icount.rx += count;
+	dma->rx_running = 0;
 
 	tty_flip_buffer_push(tty_port);
 }
@@ -62,9 +70,14 @@ static void dma_rx_complete(void *param)
 	struct uart_8250_dma *dma = p->dma;
 	unsigned long flags;
 
-	__dma_rx_complete(p);
-
 	spin_lock_irqsave(&p->port.lock, flags);
+	if (dma->rx_running)
+		__dma_rx_complete(p);
+
+	/*
+	 * Cannot be combined with the previous check because __dma_rx_complete()
+	 * changes dma->rx_running.
+	 */
 	if (!dma->rx_running && (serial_lsr_in(p) & UART_LSR_DR))
 		p->dma->rx_dma(p);
 	spin_unlock_irqrestore(&p->port.lock, flags);
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index a1490033aa16..409e91d6829a 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -797,25 +797,11 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
 		spin_unlock(&port->lock);
 	}
 
-	if (stm32_usart_rx_dma_enabled(port))
-		return IRQ_WAKE_THREAD;
-	else
-		return IRQ_HANDLED;
-}
-
-static irqreturn_t stm32_usart_threaded_interrupt(int irq, void *ptr)
-{
-	struct uart_port *port = ptr;
-	struct tty_port *tport = &port->state->port;
-	struct stm32_port *stm32_port = to_stm32_port(port);
-	unsigned int size;
-	unsigned long flags;
-
 	/* Receiver timeout irq for DMA RX */
-	if (!stm32_port->throttled) {
-		spin_lock_irqsave(&port->lock, flags);
+	if (stm32_usart_rx_dma_enabled(port) && !stm32_port->throttled) {
+		spin_lock(&port->lock);
 		size = stm32_usart_receive_chars(port, false);
-		uart_unlock_and_check_sysrq_irqrestore(port, flags);
+		uart_unlock_and_check_sysrq(port);
 		if (size)
 			tty_flip_buffer_push(tport);
 	}
@@ -1015,10 +1001,8 @@ static int stm32_usart_startup(struct uart_port *port)
 	u32 val;
 	int ret;
 
-	ret = request_threaded_irq(port->irq, stm32_usart_interrupt,
-				   stm32_usart_threaded_interrupt,
-				   IRQF_ONESHOT | IRQF_NO_SUSPEND,
-				   name, port);
+	ret = request_irq(port->irq, stm32_usart_interrupt,
+			  IRQF_NO_SUSPEND, name, port);
 	if (ret)
 		return ret;
 
@@ -1601,13 +1585,6 @@ static int stm32_usart_of_dma_rx_probe(struct stm32_port *stm32port,
 	struct dma_slave_config config;
 	int ret;
 
-	/*
-	 * Using DMA and threaded handler for the console could lead to
-	 * deadlocks.
-	 */
-	if (uart_console(port))
-		return -ENODEV;
-
 	stm32port->rx_buf = dma_alloc_coherent(dev, RX_BUF_L,
 					       &stm32port->rx_dma_buf,
 					       GFP_KERNEL);
diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index 1850bacdb5b0..f566eb1839dc 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -386,10 +386,6 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 
 	uni_mode = use_unicode(inode);
 	attr = use_attributes(inode);
-	ret = -ENXIO;
-	vc = vcs_vc(inode, &viewed);
-	if (!vc)
-		goto unlock_out;
 
 	ret = -EINVAL;
 	if (pos < 0)
@@ -407,6 +403,11 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 		unsigned int this_round, skip = 0;
 		int size;
 
+		ret = -ENXIO;
+		vc = vcs_vc(inode, &viewed);
+		if (!vc)
+			goto unlock_out;
+
 		/* Check whether we are above size each round,
 		 * as copy_to_user at the end of this loop
 		 * could sleep.