linux-kernel - [PATCH] serial: core: check if uart_get

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Date:   Sun, 29 May 2022 09:46:05 -0400
From:   Tom Rix <trix@...hat.com>
To:     gregkh@...uxfoundation.org, jirislaby@...nel.org,
        nathan@...nel.org, ndesaulniers@...gle.com,
        peter@...leysoftware.com
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Tom Rix <trix@...hat.com>
Subject: [PATCH] serial: core: check if uart_get_info succeeds before using

clang static analysis reports this representative issue
drivers/tty/serial/serial_core.c:2818:9: warning: 3rd function call argument is an uninitialized value [core.CallAndMessage]
        return sprintf(buf, "%d\n", tmp.iomem_reg_shift);
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

uart_get_info() is used the *show() functions.  When uart_get_info() fails, what is reported
is garbage.  So check if uart_get_info() succeeded.

Fixes: 4047b37122d1 ("serial: core: Prevent unsafe uart port access, part 1")
Signed-off-by: Tom Rix <trix@...hat.com>
---
 drivers/tty/serial/serial_core.c | 52 ++++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 9a85b41caa0a..4160f6711c5d 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2690,7 +2690,9 @@ static ssize_t uartclk_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.baud_base * 16);
 }
 
@@ -2700,7 +2702,9 @@ static ssize_t type_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.type);
 }
 
@@ -2710,7 +2714,9 @@ static ssize_t line_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.line);
 }
 
@@ -2721,7 +2727,9 @@ static ssize_t port_show(struct device *dev,
 	struct tty_port *port = dev_get_drvdata(dev);
 	unsigned long ioaddr;
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	ioaddr = tmp.port;
 	if (HIGH_BITS_OFFSET)
 		ioaddr |= (unsigned long)tmp.port_high << HIGH_BITS_OFFSET;
@@ -2734,7 +2742,9 @@ static ssize_t irq_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.irq);
 }
 
@@ -2744,7 +2754,9 @@ static ssize_t flags_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "0x%X\n", tmp.flags);
 }
 
@@ -2754,7 +2766,9 @@ static ssize_t xmit_fifo_size_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.xmit_fifo_size);
 }
 
@@ -2764,7 +2778,9 @@ static ssize_t close_delay_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.close_delay);
 }
 
@@ -2774,7 +2790,9 @@ static ssize_t closing_wait_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.closing_wait);
 }
 
@@ -2784,7 +2802,9 @@ static ssize_t custom_divisor_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.custom_divisor);
 }
 
@@ -2794,7 +2814,9 @@ static ssize_t io_type_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.io_type);
 }
 
@@ -2804,7 +2826,9 @@ static ssize_t iomem_base_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "0x%lX\n", (unsigned long)tmp.iomem_base);
 }
 
@@ -2814,7 +2838,9 @@ static ssize_t iomem_reg_shift_show(struct device *dev,
 	struct serial_struct tmp;
 	struct tty_port *port = dev_get_drvdata(dev);
 
-	uart_get_info(port, &tmp);
+	if (uart_get_info(port, &tmp))
+		return 0;
+
 	return sprintf(buf, "%d\n", tmp.iomem_reg_shift);
 }
 
-- 
2.27.0