Re: [net-next,v7,3/8] net: wwan: core: split port creation and registration
From: Jakub Kicinski <kuba@kernel.org>
Date: 2026-01-16 02:44:42
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This is an AI-generated review of your patch. The human sending this email has considered the AI review valid, or at least plausible. For local reproduction steps see https://netdev-ai.bots.linux.dev/ai-local.html --- net: wwan: core: split port creation and registration This patch splits the port creation function to prepare for upcoming GNSS port type support. It separates device_register() into device_initialize() and device_add(), and moves minor number allocation into the new wwan_port_register_wwan() function.
quoted hunk ↗ jump to hunk
diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c index 1da935e84008..1a9a77d597e6 100644 --- a/drivers/net/wwan/wwan_core.c +++ b/drivers/net/wwan/wwan_core.c@@ -357,7 +357,8 @@ static void wwan_port_destroy(struct device *dev) { struct wwan_port *port = to_wwan_port(dev); - ida_free(&minors, MINOR(port->dev.devt)); + if (dev->class == &wwan_class) + ida_free(&minors, MINOR(dev->devt)); mutex_destroy(&port->data_lock); mutex_destroy(&port->ops_lock); kfree(port);
[ ... ]
+/* Register a regular WWAN port device (e.g. AT, MBIM, etc.) */
+static int wwan_port_register_wwan(struct wwan_port *port)
+{
+ struct wwan_device *wwandev = to_wwan_dev(port->dev.parent);
+ char namefmt[0x20];
+ int minor, err;
+
+ /* A port is exposed as character device, get a minor */
+ minor = ida_alloc_range(&minors, 0, WWAN_MAX_MINORS - 1, GFP_KERNEL);
+ if (minor < 0)
+ return minor;
+
+ port->dev.class = &wwan_class;
+ port->dev.devt = MKDEV(wwan_major, minor);[ ... ]
+ err = device_add(&port->dev);
+
+ mutex_unlock(&wwan_register_lock);
+
+ if (err) {
+ ida_free(&minors, minor);^^^^^^^^^^^^^^^^^^^^^^^^ When device_add() fails, this frees the minor. However, port->dev.class was already set to wwan_class above, and port->dev.devt contains the minor number. The caller (wwan_create_port) then calls put_device() which triggers wwan_port_destroy(). Since dev->class == &wwan_class is true, wwan_port_destroy() calls ida_free() again on the same minor. Wouldn't this cause a double ida_free when device_add() fails? The call chain is: wwan_port_register_wwan() fails -> ida_free(minor) -> return error -> wwan_create_port() -> put_device() -> wwan_port_destroy() -> ida_free(minor) again. Maybe the class should be cleared on error before returning, or the ida_free in the error path should be removed since wwan_port_destroy() will handle it?
+ return err; + } + + dev_info(&wwandev->dev, "port %s attached\n", dev_name(&port->dev)); + + return 0; +}
[ ... ]
+ device_initialize(&port->dev); + + err = wwan_port_register_wwan(port); if (err) goto error_put_device; + return port; error_put_device: + put_device(&port->dev);
-- pw-bot: cr