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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hans de Goede <hdegoede@redhat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 194/338] ACPICA: Avoid walking the ACPI Namespace if it is not there
Date:   Thu, 14 Apr 2022 15:11:37 +0200
Message-Id: <20220414110844.417987196@linuxfoundation.org>
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

[ Upstream commit 0c9992315e738e7d6e927ef36839a466b080dba6 ]

ACPICA commit b1c3656ef4950098e530be68d4b589584f06cddc

Prevent acpi_ns_walk_namespace() from crashing when called with
start_node equal to ACPI_ROOT_OBJECT if the Namespace has not been
instantiated yet and acpi_gbl_root_node is NULL.

For instance, this can happen if the kernel is run with "acpi=off"
in the command line.

Link: https://github.com/acpica/acpica/commit/b1c3656ef4950098e530be68d4b589584f06cddc
Link: https://lore.kernel.org/linux-acpi/CAJZ5v0hJWW_vZ3wwajE7xT38aWjY7cZyvqMJpXHzUL98-SiCVQ@mail.gmail.com/
Reported-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/acpi/acpica/nswalk.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/acpica/nswalk.c b/drivers/acpi/acpica/nswalk.c
index e9a061da9bb2..c325789a62bf 100644
--- a/drivers/acpi/acpica/nswalk.c
+++ b/drivers/acpi/acpica/nswalk.c
@@ -169,6 +169,9 @@ acpi_ns_walk_namespace(acpi_object_type type,
 
 	if (start_node == ACPI_ROOT_OBJECT) {
 		start_node = acpi_gbl_root_node;
+		if (!start_node) {
+			return_ACPI_STATUS(AE_NO_NAMESPACE);
+		}
 	}
 
 	/* Null child means "get first node" */
-- 
2.34.1