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 140FF15AE3 for ; Wed, 9 Aug 2023 10:46:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 89037C433C8; Wed, 9 Aug 2023 10:46:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691577981; bh=+w5/Zduul5tnSgpVFEGA9PFKCeV/Xgi+eD0DUWXoz70=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=foNwaT4ikoM1SYW9c68vIV83FayER8hNOPFdB7nU+Q0UYKrN2ulLsnFA85fTLfWwO BkGszNqAbfg46nzL0QgYau9trNN2TPzTNcf71WP+rNrFJNNjRTAmhwDAZ1PTvrZ+kC CAHv2gkpD3UDLVJ90ZRXZujJlHmDg4KKC5WBjo2w= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Duoming Zhou , "David S. Miller" , Sasha Levin Subject: [PATCH 6.4 062/165] net: usb: lan78xx: reorder cleanup operations to avoid UAF bugs Date: Wed, 9 Aug 2023 12:39:53 +0200 Message-ID: <20230809103644.851543936@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230809103642.720851262@linuxfoundation.org> References: <20230809103642.720851262@linuxfoundation.org> User-Agent: quilt/0.67 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-Transfer-Encoding: 8bit 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") 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(-) diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c index c458c030fadf6..59cde06aa7f60 100644 --- a/drivers/net/usb/lan78xx.c +++ b/drivers/net/usb/lan78xx.c @@ -4224,8 +4224,6 @@ static void lan78xx_disconnect(struct usb_interface *intf) if (!dev) return; - set_bit(EVENT_DEV_DISCONNECT, &dev->flags); - netif_napi_del(&dev->napi); udev = interface_to_usbdev(intf); @@ -4233,6 +4231,8 @@ static void lan78xx_disconnect(struct usb_interface *intf) unregister_netdev(net); + timer_shutdown_sync(&dev->stat_monitor); + set_bit(EVENT_DEV_DISCONNECT, &dev->flags); cancel_delayed_work_sync(&dev->wq); phydev = net->phydev; @@ -4247,9 +4247,6 @@ static void lan78xx_disconnect(struct usb_interface *intf) usb_scuttle_anchored_urbs(&dev->deferred); - if (timer_pending(&dev->stat_monitor)) - del_timer_sync(&dev->stat_monitor); - lan78xx_unbind(dev, intf); lan78xx_free_tx_resources(dev); -- 2.40.1