From: Saubhik Mukherjee <saubhik.mukherjee@gmail.com>
To: gregkh@linuxfoundation.org, jirislaby@kernel.org
Cc: Saubhik Mukherjee <saubhik.mukherjee@gmail.com>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
ldv-project@linuxtesting.org, andrianov@ispras.ru
Subject: [PATCH] tty: serial: owl: Fix data race in owl_uart_remove
Date: Thu, 17 Jun 2021 16:34:43 +0530 [thread overview]
Message-ID: <20210617110443.6526-1-saubhik.mukherjee@gmail.com> (raw)
Suppose the driver is registered and a UART port is added. Once an
application opens the port, owl_uart_startup is called which registers
the interrupt handler owl_uart_irq.
We could have the following race condition:
When device is removed, owl_uart_remove is called, which calls
uart_remove_one_port, which calls owl_uart_release_port, which writes
NULL to port->membase. At this point parallely, an interrupt could be
handled by owl_uart_irq which reads port->membase.
This is because it is possible to remove device without closing a port.
Thus, we need to check it and call owl_uart_shutdown in owl_uart_remove.
Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Saubhik Mukherjee <saubhik.mukherjee@gmail.com>
---
drivers/tty/serial/owl-uart.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
index 91f1eb0058d7..ac4e3aae2719 100644
--- a/drivers/tty/serial/owl-uart.c
+++ b/drivers/tty/serial/owl-uart.c
@@ -751,8 +751,15 @@ static int owl_uart_probe(struct platform_device *pdev)
static int owl_uart_remove(struct platform_device *pdev)
{
struct owl_uart_port *owl_port = platform_get_drvdata(pdev);
+ struct uart_port *port = &owl_port->port;
- uart_remove_one_port(&owl_uart_driver, &owl_port->port);
+ /* It is possible to release device without closing a port.
+ * Thus, need to check it and call shutdown.
+ */
+ if (owl_uart_read(port, OWL_UART_CTL) & OWL_UART_CTL_EN)
+ owl_uart_shutdown(port);
+
+ uart_remove_one_port(&owl_uart_driver, port);
owl_uart_ports[pdev->id] = NULL;
clk_disable_unprepare(owl_port->clk);
--
2.30.2
next reply other threads:[~2021-06-17 11:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 11:04 Saubhik Mukherjee [this message]
2021-06-17 11:22 ` [PATCH] tty: serial: owl: Fix data race in owl_uart_remove Greg KH
2021-06-23 5:36 ` Saubhik Mukherjee
2021-06-23 7:16 ` Johan Hovold
2021-06-24 12:07 ` Saubhik Mukherjee
2021-06-24 12:29 ` Johan Hovold
2021-06-25 7:52 ` Saubhik Mukherjee
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