linux-kernel - [PATCH 45/50] pch_uart: fix a deadlock when pch

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1372763258-20664-46-git-send-email-luis.henriques@canonical.com>
Date:	Tue,  2 Jul 2013 12:07:33 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Liang Li <liang.li@...driver.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Yijing Wang <wangyijing@...wei.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 45/50] pch_uart: fix a deadlock when pch_uart as console

3.5.7.16 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Liang Li <liang.li@...driver.com>

commit 384e301e3519599b000c1a2ecd938b533fc15d85 upstream.

When we use pch_uart as system console like 'console=ttyPCH0,115200',
then 'send break' to it. We'll encounter the deadlock on a cpu/core,
with interrupts disabled on the core. When we happen to have all irqs
affinity to cpu0 then the deadlock on cpu0 actually deadlock whole
system.

In pch_uart_interrupt, we have spin_lock_irqsave(&priv->lock, flags)
then call pch_uart_err_ir when break is received. Then the call to
dev_err would actually call to pch_console_write then we'll run into
another spin_lock(&priv->lock), with interrupts disabled.

So in the call sequence lead by pch_uart_interrupt, we should be
carefully to call functions that will 'print message to console' only
in case the uart port is not being used as serial console.

Signed-off-by: Liang Li <liang.li@...driver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Yijing Wang <wangyijing@...wei.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/tty/serial/pch_uart.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 558ce85..4798e94 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1034,22 +1034,37 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
 static void pch_uart_err_ir(struct eg20t_port *priv, unsigned int lsr)
 {
 	u8 fcr = ioread8(priv->membase + UART_FCR);
+	struct uart_port *port = &priv->port;
+	struct tty_struct *tty = tty_port_tty_get(&port->state->port);
+	char   *error_msg[5] = {};
+	int    i = 0;
 
 	/* Reset FIFO */
 	fcr |= UART_FCR_CLEAR_RCVR;
 	iowrite8(fcr, priv->membase + UART_FCR);
 
 	if (lsr & PCH_UART_LSR_ERR)
-		dev_err(&priv->pdev->dev, "Error data in FIFO\n");
+		error_msg[i++] = "Error data in FIFO\n";
 
-	if (lsr & UART_LSR_FE)
-		dev_err(&priv->pdev->dev, "Framing Error\n");
+	if (lsr & UART_LSR_FE) {
+		port->icount.frame++;
+		error_msg[i++] = "  Framing Error\n";
+	}
 
-	if (lsr & UART_LSR_PE)
-		dev_err(&priv->pdev->dev, "Parity Error\n");
+	if (lsr & UART_LSR_PE) {
+		port->icount.parity++;
+		error_msg[i++] = "  Parity Error\n";
+	}
 
-	if (lsr & UART_LSR_OE)
-		dev_err(&priv->pdev->dev, "Overrun Error\n");
+	if (lsr & UART_LSR_OE) {
+		port->icount.overrun++;
+		error_msg[i++] = "  Overrun Error\n";
+	}
+
+	if (tty == NULL) {
+		for (i = 0; error_msg[i] != NULL; i++)
+			dev_err(&priv->pdev->dev, error_msg[i]);
+	}
 }
 
 static irqreturn_t pch_uart_interrupt(int irq, void *dev_id)
-- 
1.8.1.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/