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 268B94777C; Mon, 8 Jan 2024 14:52:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mRgG5hW+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4DCB4C433C7; Mon, 8 Jan 2024 14:52:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1704725548; bh=wdN+qxLwvdtOT6W/sXpFUa78ssD1EepeKJXNbsHBzuI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mRgG5hW+BKXr4DywkFqG48Vvtv1NQoyGPLh0gTgv1mGnJujs1MFUnl8KA/t1egtBu TzFTQnUdA/Nng8dovQYlXKiclk/OSqfDYjfkpLjMnyNG3P3Vsj16JPlCjKzjWSO+v4 8d4SKcMummiHZB4aQopBeKANOXQCGHNmXN3LKPxY/IpkO7Fn+fjau9PFl7czYGka9Q 7CyaL4zDBYkx1Eel8SGc4CUM0Ey/RlhFkMcFG9ISoWXaZxazuB2GnE/rpLwdE9SOes MpSwM9ppK/40LVoXVfaG6VajZK1EjrvJMZnL0MyKDr8Gsfwt6FhZZRQZEanCHY8q1b Dyt5Sqx03Y2mg== Date: Mon, 8 Jan 2024 14:52:24 +0000 From: Lee Jones To: Greg Kroah-Hartman Cc: stable@vger.kernel.org, patches@lists.linux.dev, Duoming Zhou , "David S. Miller" , Sasha Levin Subject: Re: [PATCH 6.4 062/165] net: usb: lan78xx: reorder cleanup operations to avoid UAF bugs Message-ID: <20240108145224.GA641998@google.com> References: <20230809103642.720851262@linuxfoundation.org> <20230809103644.851543936@linuxfoundation.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev 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: <20230809103644.851543936@linuxfoundation.org> On Wed, 09 Aug 2023, Greg Kroah-Hartman wrote: > From: Duoming Zhou > > [ Upstream commit 1e7417c188d0a83fb385ba2dbe35fd2563f2b6f3 ] > > The timer dev->stat_monitor can schedule the delayed work dev->wq and > the delayed work dev->wq can also arm the dev->stat_monitor timer. > > When the device is detaching, the net_device will be deallocated. but > the net_device private data could still be dereferenced in delayed work > or timer handler. As a result, the UAF bugs will happen. > > One racy situation is shown below: > > (Thread 1) | (Thread 2) > lan78xx_stat_monitor() | > ... | lan78xx_disconnect() > lan78xx_defer_kevent() | ... > ... | cancel_delayed_work_sync(&dev->wq); > schedule_delayed_work() | ... > (wait some time) | free_netdev(net); //free net_device > lan78xx_delayedwork() | > //use net_device private data | > dev-> //use | > > Although we use cancel_delayed_work_sync() to cancel the delayed work > in lan78xx_disconnect(), it could still be scheduled in timer handler > lan78xx_stat_monitor(). > > Another racy situation is shown below: > > (Thread 1) | (Thread 2) > lan78xx_delayedwork | > mod_timer() | lan78xx_disconnect() > | cancel_delayed_work_sync() > (wait some time) | if (timer_pending(&dev->stat_monitor)) > | del_timer_sync(&dev->stat_monitor); > lan78xx_stat_monitor() | ... > lan78xx_defer_kevent() | free_netdev(net); //free > //use net_device private data| > dev-> //use | > > Although we use del_timer_sync() to delete the timer, the function > timer_pending() returns 0 when the timer is activated. As a result, > the del_timer_sync() will not be executed and the timer could be > re-armed. > > In order to mitigate this bug, We use timer_shutdown_sync() to shutdown > the timer and then use cancel_delayed_work_sync() to cancel the delayed > work. As a result, the net_device could be deallocated safely. > > What's more, the dev->flags is set to EVENT_DEV_DISCONNECT in > lan78xx_disconnect(). But it could still be set to EVENT_STAT_UPDATE > in lan78xx_stat_monitor(). So this patch put the set_bit() behind > timer_shutdown_sync(). > > Fixes: 77dfff5bb7e2 ("lan78xx: Fix race condition in disconnect handling") Any idea why this stopped at linux-6.4.y? The aforementioned Fixes: commit also exists in linux-6.1.y and linux-5.15.y. I don't see any earlier backport attempts or failure reports that would otherwise explain this. > Signed-off-by: Duoming Zhou > Signed-off-by: David S. Miller > Signed-off-by: Sasha Levin > --- > drivers/net/usb/lan78xx.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) -- Lee Jones [李琼斯]