From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8F47C433F5 for ; Mon, 31 Jan 2022 10:22:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358105AbiAaKW4 (ORCPT ); Mon, 31 Jan 2022 05:22:56 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:39634 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358090AbiAaKWz (ORCPT ); Mon, 31 Jan 2022 05:22:55 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A9D3861303 for ; Mon, 31 Jan 2022 10:22:55 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6EFD4C340E8; Mon, 31 Jan 2022 10:22:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643624575; bh=J6x/1Y4vi5PSU7wHBKW0kKsd+BnRIjW1uAfo+3DT63Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=E1/+B+z+OyzbxNY1iNMxGSiRzGPgwLRPY1niIvXPpoPCXBnbRseh3qlxA8jyGntXU +okxL2MZxRlW7TJDumbOvY07hIKshKZ6O1BctNFld8kbCRxD4Cjeq3bLm6QoeoZog/ nEs4c77bGolimpGpNoeiqNxL3Eh7NYIUltzCtiVk= Date: Mon, 31 Jan 2022 11:22:52 +0100 From: Greg Kroah-Hartman To: Udipto Goswami Cc: Felipe Balbi , John Keeping , linux-usb@vger.kernel.org, Pratham Pratap , Pavankumar Kondeti , Jack Pham Subject: Re: [PATCH v10] usb: f_fs: Fix use-after-free for epfile Message-ID: References: <1643256595-10797-1-git-send-email-quic_ugoswami@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1643256595-10797-1-git-send-email-quic_ugoswami@quicinc.com> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Thu, Jan 27, 2022 at 09:39:55AM +0530, Udipto Goswami wrote: > Consider a case where ffs_func_eps_disable is called from > ffs_func_disable as part of composition switch and at the > same time ffs_epfile_release get called from userspace. > ffs_epfile_release will free up the read buffer and call > ffs_data_closed which in turn destroys ffs->epfiles and > mark it as NULL. While this was happening the driver has > already initialized the local epfile in ffs_func_eps_disable > which is now freed and waiting to acquire the spinlock. Once > spinlock is acquired the driver proceeds with the stale value > of epfile and tries to free the already freed read buffer > causing use-after-free. > > Following is the illustration of the race: > > CPU1 CPU2 > > ffs_func_eps_disable > epfiles (local copy) > ffs_epfile_release > ffs_data_closed > if (last file closed) > ffs_data_reset > ffs_data_clear > ffs_epfiles_destroy > spin_lock > dereference epfiles > > Fix this races by taking epfiles local copy & assigning it under > spinlock and if epfiles(local) is null then update it in ffs->epfiles > then finally destroy it. > Extending the scope further from the race, protecting the ep related > structures, and concurrent accesses. > > Fixes: a9e6f83c2df (usb: gadget: f_fs: stop sleeping in ffs_func_eps_disable) Nit, this should have been: Fixes: a9e6f83c2df1 ("usb: gadget: f_fs: stop sleeping in ffs_func_eps_disable") I've fixed it up now, thanks. greg k-h