[PATCH] platform/mellanox: mlxbf-pmc: Check ACPI_COMPANION() against NULL

[Linmao Li]

Every platform driver can be forced to match a device that doesn't match
its list of device IDs because of device_match_driver_override(), so
platform drivers that rely on the existence of a device's ACPI companion
object need to verify its presence.

mlxbf_pmc_probe() passes the result of ACPI_COMPANION() to
acpi_device_hid(), which dereferences it, so force-binding the driver to
a device without an ACPI companion leads to a NULL pointer dereference.

Accordingly, add a requisite ACPI_COMPANION() check against NULL to the
mlxbf-pmc driver and return -ENODEV when the companion is missing.

Fixes: 1a218d312e65 ("platform/mellanox: mlxbf-pmc: Add Mellanox BlueField PMC driver")
Signed-off-by: Linmao Li <lilinmao@xxxxxxxxxx>
---
 drivers/platform/mellanox/mlxbf-pmc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/mellanox/mlxbf-pmc.c b/drivers/platform/mellanox/mlxbf-pmc.c
index 5ec1ad471696..2ad9e2b0493c 100644
--- a/drivers/platform/mellanox/mlxbf-pmc.c
+++ b/drivers/platform/mellanox/mlxbf-pmc.c
@@ -2262,13 +2262,19 @@ static int mlxbf_pmc_map_counters(struct device *dev)
 
 static int mlxbf_pmc_probe(struct platform_device *pdev)
 {
-	struct acpi_device *acpi_dev = ACPI_COMPANION(&pdev->dev);
-	const char *hid = acpi_device_hid(acpi_dev);
 	struct device *dev = &pdev->dev;
+	struct acpi_device *acpi_dev;
 	struct arm_smccc_res res;
+	const char *hid;
 	guid_t guid;
 	int ret;
 
+	acpi_dev = ACPI_COMPANION(&pdev->dev);
+	if (!acpi_dev)
+		return -ENODEV;
+
+	hid = acpi_device_hid(acpi_dev);
+
 	/* Ensure we have the UUID we expect for this service. */
 	arm_smccc_smc(MLXBF_PMC_SIP_SVC_UID, 0, 0, 0, 0, 0, 0, 0, &res);
 	guid_parse(mlxbf_pmc_svc_uuid_str, &guid);
-- 
2.25.1