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From:   Tong Zhang <ztong0001@gmail.com>
To:     Benson Leung <bleung@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        linux-kernel@vger.kernel.org
Cc:     Tong Zhang <ztong0001@gmail.com>
Subject: [PATCH] platform/chrome: cros_ec: honor acpi=off
Date:   Tue, 15 Feb 2022 22:26:01 -0800
Message-Id: <20220216062601.779690-1-ztong0001@gmail.com>
MIME-Version: 1.0
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when acpi=off is provided in bootarg, kernel crash with

 BUG: kernel NULL pointer dereference, address: 0000000000000018
 RIP: 0010:acpi_ns_walk_namespace+0x57/0x280
  <TASK>
 ? acpi_get_devices+0x140/0x140
 cros_ec_lpc_init+0x25/0x100

Driver should check if ACPI is disabled before calling acpi_get_devices(),
otherwise acpi_walk_namespace() will dereference null pointer since the
acpi_gbl_root_node is not initialized.
This is a common pattern and should be fixed in ACPI framework to prevent
such crash in the future, but since many drivers are already doing explicit
check(acpi_disable) we do the same thing here.

Signed-off-by: Tong Zhang <ztong0001@gmail.com>
---
 drivers/platform/chrome/cros_ec_lpc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
index d6306d2a096f..95412a55ed8d 100644
--- a/drivers/platform/chrome/cros_ec_lpc.c
+++ b/drivers/platform/chrome/cros_ec_lpc.c
@@ -550,6 +550,9 @@ static int __init cros_ec_lpc_init(void)
 	int ret;
 	acpi_status status;
 
+	if (acpi_disable)
+		return -ENODEV;
+
 	status = acpi_get_devices(ACPI_DRV_NAME, cros_ec_lpc_parse_device,
 				  &cros_ec_lpc_acpi_device_found, NULL);
 	if (ACPI_FAILURE(status))
-- 
2.25.1