On sc7180-trogdor class devices with 'fw_devlink=permissive' and KASAN
enabled, you'll see a Use-After-Free reported at bootup.
The root of the problem is that dwc3_qcom_of_register_core() is adding
a devm-allocated "tx-fifo-resize" property to its device tree node
using of_add_property().
The issue is that of_add_property() makes a _permanent_ addition to
the device tree that lasts until reboot. That means allocating memory
for the property using "devm" managed memory is a terrible idea since
that memory will be freed upon probe deferral or device
unbinding. Let's change to just allocate memory once and never free
it. This sorta looks like a leak but isn't truly one, since only one
property will be allocated per device tree node per boot.
NOTE: one would think that perhaps it would be better to use
of_remove_property() and then be able to free the property on device
remove. That sounds good until you read the comments for
of_remove_property(), which says that properties are never really
removed and they're just moved to the side.
Fixes: cefdd52fa045 ("usb: dwc3: dwc3-qcom: Enable tx-fifo-resize property by default")
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
drivers/usb/dwc3/dwc3-qcom.c | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)
diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index 9abbd01028c5..34b054033116 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -658,18 +658,28 @@ static int dwc3_qcom_of_register_core(struct platform_device *pdev)
return -ENODEV;
}
- prop = devm_kzalloc(dev, sizeof(*prop), GFP_KERNEL);
- if (!prop) {
- ret = -ENOMEM;
- dev_err(dev, "unable to allocate memory for property\n");
- goto node_put;
- }
+ /*
+ * Permanently add the "tx-fifo-resize" to the device tree. Even if
+ * our device is unregistered this property will still be part
+ * of the device tree until reboot. Because this is a "permanent"
+ * change, we allocate memory _without_ devm. For some context, see
+ * the fact that of_remove_property() doesn't actually remove things.
+ */
+ if (!of_find_property(dwc3_np, "tx-fifo-resize", NULL)) {
+ prop = kzalloc(sizeof(*prop), GFP_KERNEL);
+ if (!prop) {
+ ret = -ENOMEM;
+ dev_err(dev, "unable to allocate memory for property\n");
+ goto node_put;
+ }
- prop->name = "tx-fifo-resize";
- ret = of_add_property(dwc3_np, prop);
- if (ret) {
- dev_err(dev, "unable to add property\n");
- goto node_put;
+ prop->name = "tx-fifo-resize";
+ ret = of_add_property(dwc3_np, prop);
+ if (ret) {
+ dev_err(dev, "unable to add property\n");
+ kfree(prop);
+ goto node_put;
+ }
}
ret = of_platform_populate(np, NULL, NULL, dev);
--
2.34.1.400.ga245620fadb-goog
