linux-kernel - [PATCH] ACPI: OSL: Fix and clean up acpi_os_read/write

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Date:   Wed, 12 Jan 2022 19:31:48 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Dan Carpenter <dan.carpenter@...il.com>
Subject: [PATCH] ACPI: OSL: Fix and clean up acpi_os_read/write_port()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

First, remove type casts that make acpi_os_read_port() only work on
little endian and are generally not needed.

Second, avoid clearing the memory pointed to by the value return
pointer in acpi_os_read_port() if it is the dummy on the stack (in
which case clearing it is not necessary).

Finally, prevent both acpi_os_read_port() and acpi_os_write_port()
from crashing the kernel when they receive an unsupported width
value and make them print a debug message and return an error instead.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/acpi/osl.c |   19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

Index: linux-pm/drivers/acpi/osl.c
===================================================================
--- linux-pm.orig/drivers/acpi/osl.c
+++ linux-pm/drivers/acpi/osl.c
@@ -642,22 +642,24 @@ u64 acpi_os_get_timer(void)
 		(ACPI_100NSEC_PER_SEC / HZ);
 }
 
-acpi_status acpi_os_read_port(acpi_io_address port, u32 * value, u32 width)
+acpi_status acpi_os_read_port(acpi_io_address port, u32 *value, u32 width)
 {
 	u32 dummy;
 
-	if (!value)
+	if (value)
+		*value = 0;
+	else
 		value = &dummy;
 
-	*value = 0;
 	if (width <= 8) {
-		*(u8 *) value = inb(port);
+		*value = inb(port);
 	} else if (width <= 16) {
-		*(u16 *) value = inw(port);
+		*value = inw(port);
 	} else if (width <= 32) {
-		*(u32 *) value = inl(port);
+		*value = inl(port);
 	} else {
-		BUG();
+		pr_debug("%s: Access width %d not supported\n", __func__, width);
+		return AE_BAD_PARAMETER;
 	}
 
 	return AE_OK;
@@ -674,7 +676,8 @@ acpi_status acpi_os_write_port(acpi_io_a
 	} else if (width <= 32) {
 		outl(value, port);
 	} else {
-		BUG();
+		pr_debug("%s: Access width %d not supported\n", __func__, width);
+		return AE_BAD_PARAMETER;
 	}
 
 	return AE_OK;