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 0F75036D4E6 for ; Thu, 27 Nov 2025 09:16:03 +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=1764234965; cv=none; b=dChK3ftoJdSmx2FfbwGUEWseFg3zZlkruW6deg/cfErR/4GsLIdKeGkc3TYM34nOzcz7R+8/WrhE50yqQLrr6epQBdLpXrIbm+oOt3Xzd3UW3d4bWQmCvTWybuyhZlQQ+QvIKx8Yb4N/jOyqZYeH3QNcK6g74NUwlsr7nLlJZaE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764234965; c=relaxed/simple; bh=OipEW4orNVdq5kw+X5CCgPxjTXoKXMDi7Z0lPDcDU1E=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kSwUSedZmRqM2GDrbdL8hvFQEg1KQ4f1OG3lHdpmaiAQDs9jmGtdzSFvDUuLFpPrtRMOPL1m7HbfHeiA/qi9bCcfPabmSSErjWfrvtVlJrwUVm8tRqJchv727jw1mYUnRnsFzkBW+0cImhSJ2hxncJdSjH4fVELlUO4h9a+PooE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=tqRHKoMR; 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="tqRHKoMR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 45C2AC4CEF8; Thu, 27 Nov 2025 09:16:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764234963; bh=OipEW4orNVdq5kw+X5CCgPxjTXoKXMDi7Z0lPDcDU1E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=tqRHKoMRpMZtm0y6/W00+OPokDb3Ut/4uDZScyCto2RV3/0ZmjVEg1YbDgKtZUMdG mqH/DNlhg6C+fIrnDIQ8rlxEUtteXSW0jkS4vTBx+iaR4kMZGIUA8P3vZ6iW/9UOju njYGRScGAR8Ez27gh8FGE9j80XHygcvxvD9Jii3A= Date: Thu, 27 Nov 2025 10:16:01 +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: <2025112726-directly-underfeed-fb07@gregkh> References: <20251126160011.11649-1-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: <20251126160011.11649-1-hanguidong02@gmail.com> 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. thanks, greg k-h