Re: FAILED: patch "[PATCH] serial: 8250: of: Fix mapped region size when using" failed to apply to 4.14-stable tree

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

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Hi Greg,

On Sat, Jan 29, 2022 at 04:56:16PM +0100, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.14-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

Here is the backport.

--
Regards
Sudip

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From 51513bebad1b1d47f2ebbe52f52de971ad2835d3 Mon Sep 17 00:00:00 2001
From: Robert Hancock <robert.hancock@calian.com>
Date: Wed, 12 Jan 2022 13:42:14 -0600
Subject: [PATCH] serial: 8250: of: Fix mapped region size when using
 reg-offset property

commit d06b1cf28297e27127d3da54753a3a01a2fa2f28 upstream.

8250_of supports a reg-offset property which is intended to handle
cases where the device registers start at an offset inside the region
of memory allocated to the device. The Xilinx 16550 UART, for which this
support was initially added, requires this. However, the code did not
adjust the overall size of the mapped region accordingly, causing the
driver to request an area of memory past the end of the device's
allocation. For example, if the UART was allocated an address of
0xb0130000, size of 0x10000 and reg-offset of 0x1000 in the device
tree, the region of memory reserved was b0131000-b0140fff, which caused
the driver for the region starting at b0140000 to fail to probe.

Fix this by subtracting reg-offset from the mapped region size.

Fixes: b912b5e2cfb3 ([POWERPC] Xilinx: of_serial support for Xilinx uart 16550.)
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Robert Hancock <robert.hancock@calian.com>
Link: https://lore.kernel.org/r/20220112194214.881844-1-robert.hancock@calian.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/tty/serial/8250/8250_of.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
index c51044ba503c..0e83ce81ca33 100644
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -102,8 +102,17 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 	port->mapsize = resource_size(&resource);
 
 	/* Check for shifted address mapping */
-	if (of_property_read_u32(np, "reg-offset", &prop) == 0)
+	if (of_property_read_u32(np, "reg-offset", &prop) == 0) {
+		if (prop >= port->mapsize) {
+			dev_warn(&ofdev->dev, "reg-offset %u exceeds region size %pa\n",
+				 prop, &port->mapsize);
+			ret = -EINVAL;
+			goto err_unprepare;
+		}
+
 		port->mapbase += prop;
+		port->mapsize -= prop;
+	}
 
 	/* Compatibility with the deprecated pxa driver and 8250_pxa drivers. */
 	if (of_device_is_compatible(np, "mrvl,mmp-uart"))
-- 
2.30.2