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 944FB231A23 for ; Thu, 27 Nov 2025 15:21:17 +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=1764256878; cv=none; b=kh2Mb9f8gUfVcdhU6mbeCp2EFmvjO6r2y1XpcrYJIoegXJ4ont9TcrlC8YAeaO7I58jf++LFSJGUwYwX3y/veECxLHYtj3B/0pqvnFOzz9VHgkU4ABDAND1CUrDhButvC4zWs88tURR8WQPEj4NDKbjeRo/Ap3uHB+whJkblpYM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764256878; c=relaxed/simple; bh=070CyOdxvQMgsTEm7QHJQSsJntwumc8W0cj1UmnIYbk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=E8mAsWlmFrfGaGcrEnluHWdEOrODxwJsQ5yL4j9Bl+3WMVUiQkHbbQ9ZyxTIcdWJVuvwYY9JaqR0ZujUjC5Mb7UJY3lMnGBkwciENWynMXg21weU/i2N0iJGEE/WtGc24FbsIs6x+sLq6+Tnu/PoBLSz0IeO72iBq1ZIIv++YRs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0mYQv2lR; 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="0mYQv2lR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65FC0C4CEF8; Thu, 27 Nov 2025 15:21:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764256877; bh=070CyOdxvQMgsTEm7QHJQSsJntwumc8W0cj1UmnIYbk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=0mYQv2lRJbT9xmD2BF0ZBPlMH4RggW5aM62yKmFpeBlDctqzQDDsP0iN2+pDDfa26 mRSeenBxvODoV45GeJjOohdkhlXRNoXS9T0CwsVJT+yQqkTDFCcaMb+SalWJJz+Kre wY1CLe304d5reKNm57owIexVCJ8wZFEomXkJVavc= Date: Thu, 27 Nov 2025 16:21:15 +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 v2] driver core: fix use-after-free of driver_override via driver_match_device() Message-ID: <2025112735-pedicure-nag-558b@gregkh> References: <20251126160011.11649-1-hanguidong02@gmail.com> <2025112726-directly-underfeed-fb07@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 Thu, Nov 27, 2025 at 11:00:16PM +0800, Gui-Dong Han wrote: > On Thu, Nov 27, 2025 at 5:16 PM Greg KH wrote: > > > > On Thu, Nov 27, 2025 at 12:00:11AM +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. Also add a lock assertion to driver_match_device() to prevent future > > > locking regressions. > > > > > > 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 > > > --- > > > v2: > > > * Add device_lock_assert() in driver_match_device() to enforce locking > > > requirement, as suggested by Greg KH. > > > v1: > > > * 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/base.h | 2 ++ > > > drivers/base/bus.c | 17 ++++++++++++----- > > > drivers/base/dd.c | 3 +++ > > > 3 files changed, 17 insertions(+), 5 deletions(-) > > > > > > diff --git a/drivers/base/base.h b/drivers/base/base.h > > > index 86fa7fbb3548..011e910a53f8 100644 > > > --- a/drivers/base/base.h > > > +++ b/drivers/base/base.h > > > @@ -166,6 +166,8 @@ void device_set_deferred_probe_reason(const struct device *dev, struct va_format > > > static inline int driver_match_device(const struct device_driver *drv, > > > struct device *dev) > > > { > > > + /* Protects against driver_set_override() races */ > > > + device_lock_assert(dev); > > > return drv->bus->match ? drv->bus->match(dev, drv) : 1; > > > > A new line after the assert? > > > > And thanks for adding the comment, but: > > > > > } > > > > > > 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 */ > > > > This comment isn't needed anymore. > > > > > + device_lock(dev); > > > + ret = driver_match_device(drv, dev); > > > + device_unlock(dev); > > > + if (ret) { > > > + err = device_driver_attach(drv, dev); > > > + if (!err) { > > > + /* success */ > > > + err = count; > > > + } > > > } > > > } > > > put_device(dev); > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > > index 13ab98e033ea..db60b4500136 100644 > > > --- a/drivers/base/dd.c > > > +++ b/drivers/base/dd.c > > > @@ -1170,7 +1170,10 @@ static int __driver_attach(struct device *dev, void *data) > > > * is an error. > > > */ > > > > > > + /* Protects against driver_set_override() races */ > > > > Nor is this one. > > > > Also, I looked again, and why are you not grabbing the lock in the > > bind_store() sysfs call? driver_match_device() is only called in 3 > > places, 2 now have the lock held, and one does not. This feels wrong. > > Actually, the change in drivers/base/bus.c is exactly for the > bind_store() path. So all 3 call sites are covered and locked with > this patch. Ugh, nevermind, your patch changes bind_store() I missed that, my fault :( > I have verified this with the PoC for bind_store(), and the new > lockdep assertion does not trigger any warnings, confirming the lock > is properly held. Makes sense, thanks! I'll queue up your patch after 6.19-rc1 is out, thanks! greg k-h