linux-kernel - [PATCH] ACPI / util: cast data to u64 before shifting to fix sign extension

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Message-Id: <1458313681-24239-1-git-send-email-colin.king@canonical.com>
Date:	Fri, 18 Mar 2016 15:08:01 +0000
From:	Colin King <colin.king@...onical.com>
To:	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>, linux-acpi@...r.kernel.org,
	devel@...ica.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] ACPI / util: cast data to u64 before shifting to fix sign extension

From: Colin Ian King <colin.king@...onical.com>

obj->buffer.pointer[i] should be cast to u64 to prevent an unintentional
sign extension.  For example, if pointer[7] is 0x80, then the value
0xffffffffff000000 is or'd into mask rather than the intended value
0xff00000000000000

Detected with static analysis by CoverityScan

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/acpi/utils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index f12a724..050673f 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -692,7 +692,7 @@ bool acpi_check_dsm(acpi_handle handle, const u8 *uuid, int rev, u64 funcs)
 		mask = obj->integer.value;
 	else if (obj->type == ACPI_TYPE_BUFFER)
 		for (i = 0; i < obj->buffer.length && i < 8; i++)
-			mask |= (((u8)obj->buffer.pointer[i]) << (i * 8));
+			mask |= (((u64)obj->buffer.pointer[i]) << (i * 8));
 	ACPI_FREE(obj);
 
 	/*
-- 
2.7.3