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 7021E32721F for ; Wed, 26 Nov 2025 12:28:44 +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=1764160124; cv=none; b=M0cnywPFidVL4LILy3eCge6R3H+4zKUh2xAoJ4qBpjOAZdTptSWgicGhrgQbIOAVc40ws3sdta2FfOwjf4LT+nkKQidJxT27D048R+v0uR1k81nIOS3kWq3rwv8yjmSzYfyT2qOSbr6GjHq2BOBW5NMFPHWKgoIwV9HTFzUXGdM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764160124; c=relaxed/simple; bh=IM3/HEJ3cyMW2jdxt6OV1ZGXRJg0AbAoLQBnJrELoI8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rwgnBeOfuLG3Jq4PXhN4fV2oev1KqSBiI8CXa7vP1um6MPSkobkj7CoiXxdySVx7XhsFhlVZeKPZca5Y2ZeHUlKW1efo/uEA3zrYc27OI5xnAOxcVJm0J5AScRONPCuH2Vy/Edl5zI5mAq0Q/f+THB8aeE+7mIpBCpygDS5NZyg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=uI8DXceB; 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="uI8DXceB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8E4C6C113D0; Wed, 26 Nov 2025 12:28:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764160123; bh=IM3/HEJ3cyMW2jdxt6OV1ZGXRJg0AbAoLQBnJrELoI8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uI8DXceB5HxH0KdOvQA1MxgFs1D54KwUxvzIQcB0QwmShGWUEzZ+kho07LUCBKAhl OufI7EH0F93D7ANn+au02JrYp7xLG0S3B4HWcV58LQN7mFjo1mmfBcgu2552GPovhi wDyNoI4h2tPxYpbdzOMXv4YWIbt0POWdsmExq4Sc= Date: Wed, 26 Nov 2025 13:28:41 +0100 From: Greg KH To: Gui-Dong Han Cc: rafael@kernel.org, dakr@kernel.org, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, Qiu-ji Chen Subject: Re: [PATCH] driver core: fix use-after-free of driver_override via driver_match_device() Message-ID: <2025112659-swooned-anchovy-272a@gregkh> References: <20251126113006.9925-1-hanguidong02@gmail.com> <2025112655-ardently-abreast-23c7@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@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 Wed, Nov 26, 2025 at 07:55:06PM +0800, Gui-Dong Han wrote: > On Wed, Nov 26, 2025 at 7:39 PM Greg KH wrote: > > > > On Wed, Nov 26, 2025 at 07:30:06PM +0800, Gui-Dong Han wrote: > > > driver_set_override() modifies and frees dev->driver_override while > > > holding device_lock(dev). However, driver_match_device() reads > > > dev->driver_override when calling bus match functions. > > > > > > Currently, driver_match_device() is called from three sites. One site > > > (__device_attach_driver) holds device_lock(dev), but the other two > > > (bind_store and __driver_attach) do not. This allows a concurrent > > > driver_set_override() to free the string while driver_match_device() is > > > using it, leading to a use-after-free (UAF). > > > > > > This issue affects at least 11 bus types (including PCI, AMBA, Platform) > > > that rely on driver_override for matching. > > > > > > Fix this by holding device_lock(dev) around the driver_match_device() calls > > > in bind_store() and __driver_attach(). This ensures all access to > > > dev->driver_override via driver_match_device() is protected by the device > > > lock. > > > > > > Tested with the PoCs from Bugzilla that trigger this UAF. Stress testing > > > the two newly locked paths for 24 hours with CONFIG_PROVE_LOCKING and > > > CONFIG_LOCKDEP enabled showed no UAF recurrence and no lockdep > > > warnings. > > > > > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220789 > > > Suggested-by: Qiu-ji Chen > > > Signed-off-by: Gui-Dong Han > > > --- > > > The Bugzilla entry contains full KASAN reports and two PoCs that reliably > > > reproduce the UAF on both unlocked paths using a standard QEMU setup > > > (default e1000 device at 0000:00:03.0). > > > I chose to fix this in the driver core for the following reasons: > > > 1. Both racing functions are part of the driver core. > > > 2. Fixing this per-driver/per-bus is tedious and would require careful > > > ad-hoc locking that does not align with the existing device_lock(dev). > > > 3. We cannot simply add device_lock(dev) inside bus match functions because > > > one call path (__device_attach_driver) already holds this lock. Adding the > > > lock inside the match callback would cause a deadlock on that path. > > > --- > > > drivers/base/bus.c | 17 ++++++++++++----- > > > drivers/base/dd.c | 3 +++ > > > 2 files changed, 15 insertions(+), 5 deletions(-) > > > > > > diff --git a/drivers/base/bus.c b/drivers/base/bus.c > > > index 5e75e1bce551..9e62d6009058 100644 > > > --- a/drivers/base/bus.c > > > +++ b/drivers/base/bus.c > > > @@ -261,13 +261,20 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf, > > > const struct bus_type *bus = bus_get(drv->bus); > > > struct device *dev; > > > int err = -ENODEV; > > > + int ret; > > > > > > dev = bus_find_device_by_name(bus, NULL, buf); > > > - if (dev && driver_match_device(drv, dev)) { > > > - err = device_driver_attach(drv, dev); > > > - if (!err) { > > > - /* success */ > > > - err = count; > > > + if (dev) { > > > + /* Protects against driver_set_override() races */ > > > + device_lock(dev); > > > + ret = driver_match_device(drv, dev); > > > + device_unlock(dev); > > > > Why not have driver_match_device() take the lock instead? This way > > looks like an "anti-pattern" that we will get wrong over time. > > The reason I did not put the lock inside driver_match_device() is that > one of its existing callers, __device_attach_driver(), already holds > device_lock(dev). Unconditionally adding the lock inside > driver_match_device() would cause a deadlock on that path. Ok, then we should add a lockdep check that this specific lock is grabbed in that function so that we don't forget that this is a requirement now. > To address this and move the locking inside as you suggested, I would > need to modify the signature of driver_match_device() to accept a > flag, for example: > int driver_match_device(struct device_driver *drv, struct device *dev, > bool locked) No, that way lies madness, never do that :) thanks, greg k-h