linux-kernel - [PATCH v2 2/2] of: property: Do not link to disabled devices

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Message-Id: <20200417165442.1856-3-nsaenzjulienne@suse.de>
Date:   Fri, 17 Apr 2020 18:54:42 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     saravanak@...gle.com, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     devicetree@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Subject: [PATCH v2 2/2] of: property: Do not link to disabled devices

When creating a consumer/supplier relationship between two devices,
make sure the supplier node is actually active. Otherwise this will
create a link relationship that will never be fulfilled. This, in the
worst case scenario, will hang the system during boot.

Note that, in practice, the fact that a device-tree represented
consumer/supplier relationship isn't fulfilled will not prevent devices
from successfully probing.

Fixes: a3e1d1a7f5fc ("of: property: Add functional dependency link from DT bindings")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>

---

Changes since v1:
 - Move availability check into the compatible search routine and bail
   if device node disabled

 drivers/of/property.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index dc034eb45defd..14b6266dd054b 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1045,8 +1045,25 @@ static int of_link_to_phandle(struct device *dev, struct device_node *sup_np,
 	 * Find the device node that contains the supplier phandle.  It may be
 	 * @sup_np or it may be an ancestor of @sup_np.
 	 */
-	while (sup_np && !of_find_property(sup_np, "compatible", NULL))
+	while (sup_np) {
+
+		/*
+		 * Don't allow linking a device node as consumer of a disabled
+		 * node.
+		 */
+		if (!of_device_is_available(sup_np)) {
+			dev_dbg(dev, "Not linking to %pOFP - Not available\n",
+				sup_np);
+			of_node_put(sup_np);
+			return -ENODEV;
+		}
+
+		if (of_find_property(sup_np, "compatible", NULL))
+			break;
+
 		sup_np = of_get_next_parent(sup_np);
+	}
+
 	if (!sup_np) {
 		dev_dbg(dev, "Not linking to %pOFP - No device\n", tmp_np);
 		return -ENODEV;
-- 
2.26.0