linux-kernel - [PATCH] RFC: platform/x86: wmi: Fix check for method instance number

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Date:   Sat, 27 May 2017 13:55:34 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pali Rohár <pali.rohar@...il.com>
Subject: [PATCH] RFC: platform/x86: wmi: Fix check for method instance number

instance_count defines number of instances of data block and instance
itself is indexed from zero, which means first instance has number 0.
Therefore check for invalid instance should be non-strict inequality.

Signed-off-by: Pali Rohár <pali.rohar@...il.com>
---
I'm marking this patch as RFC because it is not tested at all and probably
could break existing WMI drivers. Some WMI drivers pass instance number 1
and I'm not sure if ACPI-WMI bytecode for those machines has really two
instances. In more cases ACPI-WMI bytecode does not check instance number
if supports only one instance. So then any instance id can be used for
correct execution of ACPI-WMI method.

So this patch is open for discussion.
---
 drivers/platform/x86/wmi.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index cd7045f..df63037 100644
--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -191,7 +191,7 @@ acpi_status wmi_evaluate_method(const char *guid_string, u8 instance,
 	if (!(block->flags & ACPI_WMI_METHOD))
 		return AE_BAD_DATA;
 
-	if (block->instance_count < instance)
+	if (block->instance_count <= instance)
 		return AE_BAD_PARAMETER;
 
 	input.count = 2;
@@ -250,7 +250,7 @@ struct acpi_buffer *out)
 	block = &wblock->gblock;
 	handle = wblock->handle;
 
-	if (block->instance_count < instance)
+	if (block->instance_count <= instance)
 		return AE_BAD_PARAMETER;
 
 	/* Check GUID is a data block */
@@ -323,7 +323,7 @@ acpi_status wmi_set_block(const char *guid_string, u8 instance,
 	block = &wblock->gblock;
 	handle = wblock->handle;
 
-	if (block->instance_count < instance)
+	if (block->instance_count <= instance)
 		return AE_BAD_PARAMETER;
 
 	/* Check GUID is a data block */
-- 
1.7.9.5