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 B801326F28D for ; Wed, 26 Nov 2025 11:39:46 +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=1764157186; cv=none; b=Mvvl7RKYfh1SCYbr05gdTdUqZ1VfoMDPUhQSQ/YnHJclPvcE0pr7ewSMk9AwEyaisqvCyq7ekCv9QcBmOX9PNjqmFB8ias7RANb6AR0vwHfDA7ntWt36M1nRjeQtPzUUCsrplx91KVsCTGeiBPVUbjSLmQc7r5NSwLGb+ElmGos= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764157186; c=relaxed/simple; bh=C9eN7cT04wsZW1ZUzoiz8C+6Jyh8zswtP7PDktZE7Jk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=pVDaYPbRzeYlGj5Rp3Nb9oYr9rK/Jnf//Hq4H9WAC30WKPbXemXpzBbD6faAWwX/CX51gMR1C2i9TKMT2eOKMpvkARvcMUQlhjjcxsZV06t5zpLjgL15aG+p5Y2BjHxx9sooA3LqcFDc2eRLNhvXobMmZqoOHpsuccT9r+tGq/s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=a8osjHgk; 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="a8osjHgk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8401C116C6; Wed, 26 Nov 2025 11:39:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764157186; bh=C9eN7cT04wsZW1ZUzoiz8C+6Jyh8zswtP7PDktZE7Jk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=a8osjHgkvl1EQmDURhZq706pxwgJyfXWAKWsn/RNa3JQW36JnO7Wux1oMSD3tLLVn YkyCyJumr0aLaeolZk6nsK4MglYy9qB8IZmDm2VaUypl+UYYggNbBP05oS6m/gOIEu EoRgRcS3RlzL0qj17ssQi0q1N8mJxtn76AbXK0Ys= Date: Wed, 26 Nov 2025 12:39:43 +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: <2025112655-ardently-abreast-23c7@gregkh> References: <20251126113006.9925-1-hanguidong02@gmail.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20251126113006.9925-1-hanguidong02@gmail.com> 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. thanks, greg k-h