From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FC5B221542; Thu, 15 Jan 2026 06:34:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768458866; cv=none; b=fCc6lgRx7ajmUXKy2IqCZCPBG32nleB4GZXfm/yZ+mb0TktG4PVEigxH6uU+ZFhRchXNPaFjTYYwLG6mWE6AHW9xJLHh6DrjY1nNpaEG4ppa669x2dKNuk+om5ZhmQ4kmXgS2FnKefmNyl4JD/neoPFVOChQHA5QiLZohKsSkhA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768458866; c=relaxed/simple; bh=/e1LEyBe3Tk2wtMsK3QUbqJijJYCaPlJd08TOwvSul0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bIxMk2njb5Hb2jNebIbRvYBv4tkqLSgHcoizvfu+yNZHMHMimc5FKkE3hGKjNw0LbK7z4o2PlX8HdPRiq9L5no5ZhPmMtcoA5bTLO5C7ZpHWMdCbHJ2sDh0SK8rc04HU+v7/kGZnHTaqGEi1X/EqX1zS8vcDUvLXSDKgb+FheUA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=slEBXcIP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="slEBXcIP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1731EC116D0; Thu, 15 Jan 2026 06:34:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1768458865; bh=/e1LEyBe3Tk2wtMsK3QUbqJijJYCaPlJd08TOwvSul0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=slEBXcIPEz5+5HCaY+ZNb7DRUSqsRtNB2nSF9mHKG8I07QUVTUk/x5OCfw77cBJIX eu1xXKGq1NgGEvC8AlH4OTT6VzvsvID2kY1IVxVrO0ojGbIhy6RgDq7U4LtTXIy9ad kxsAvY3ERQ9YLbCYxDTw7sIGfVC2KWQJqqVUVDRQ= Date: Thu, 15 Jan 2026 07:34:19 +0100 From: Greg KH To: =?utf-8?B?6b2Q5p+v5a6H?= Cc: heikki.krogerus@linux.intel.com, andersson@kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] usb: typec: mux: fix NULL pointer dereference in {typec_switch,mux}_put Message-ID: <2026011554-chute-sloppily-34bb@gregkh> References: Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Jan 15, 2026 at 02:56:24AM +0800, 齐柯宇 wrote: > This fix was discovered through static code analysis. > > In typec_switch_put() and typec_mux_put(), the code directly dereferences > sw_dev->dev.parent->driver->owner without checking if 'driver' is NULL. > This can lead to a NULL pointer dereference kernel crash. > > [Call Chain Analysis] > The vulnerable functions are called through the following paths: > > Acquisition path (fwnode_typec_switch_get): > typec_port_register() [class.c] > -> typec_switch_get() [typec_mux.h] > -> fwnode_typec_switch_get() [mux.c] > -> class_find_device() (gets device reference) > -> try_module_get(sw_devs[i]->dev.parent->driver->owner) > -> stores to sw->sw_devs[i] > > Release path (typec_switch_put): > typec_release() [class.c] > -> typec_switch_put() [mux.c] > -> module_put(sw_dev->dev.parent->driver->owner) <- BUG! > -> put_device(&sw_dev->dev) > > Registration path (typec_switch_register): > I2C/Platform driver probe() > -> typec_switch_register(dev, &sw_desc) [mux.c] > -> sw_dev->dev.parent = parent (sets parent device) > -> device_add(&sw_dev->dev) > > [Data Flow Analysis] > The critical data flow is: > > sw_dev->dev.parent: > - Set by typec_switch_register() from the 'parent' parameter > - Typically an I2C or Platform device (e.g., &client->dev) > > sw_dev->dev.parent->driver: > - Managed by kernel driver model (drivers/base/dd.c) > - Set to driver pointer when driver binds (really_probe) > - Set to NULL when driver unbinds (__device_release_driver) > > [Race Condition Scenario] > The vulnerability can be triggered by the following race condition: > > Thread A (normal operation) Thread B (attacker/event) > ---------------------------- ------------------------- > T1: typec_port_register() > T2: fwnode_typec_switch_get() > T3: try_module_get(parent->driver->owner) > T4: store sw_devs[i] > ... > T5: echo > unbind > T6: device_driver_detach() Are you sure that at this point things don't get synced up? > T7: parent->driver = NULL > T8: typec_switch_put(sw) > T9: module_put(parent->driver->owner) > -> NULL pointer dereference! A parent should never be null. > > [User-Triggerable Paths] > Users can trigger this vulnerability through: It's not a "vulnerability" given the definition of that word. > 1. sysfs unbind interface (requires root): > # echo "" > /sys/bus/i2c/drivers//unbind > > 2. Module unloading (requires root): > # rmmod > > 3. USB Type-C hot-unplug (physical access): > Physically removing the USB-C device or its parent device I don't think that removing the device can cause this, have you tried? What AI tool wrote this? You always have to document your tools, right? thanks, greg k-h