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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 641A5C432C3 for ; Fri, 15 Nov 2019 08:20:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3783A2073C for ; Fri, 15 Nov 2019 08:20:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573806026; bh=H8/ptq9B4Ies/NmvPzkI+OvZqdjM6J5mCWh0lRahEfM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Q+X/DBGDY7ODDd46a9GBbztztkbZzfbSfmF45zVLQuyKq6+a9RIu4wZFIgqLFNrmP ZGA+Fkxv11/S0Z2IEl9ECYVAXpvvpMbwCQKL6ZzCd3Wjsk5knTG5yyPctD6NV9yOuF ddmr+ukLYPiV/rRVhCUSY/RepauU1JZ/BDVR6Rd8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727199AbfKOIUZ (ORCPT ); Fri, 15 Nov 2019 03:20:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:55374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726196AbfKOIUZ (ORCPT ); Fri, 15 Nov 2019 03:20:25 -0500 Received: from localhost (unknown [104.132.150.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D6C232073C; Fri, 15 Nov 2019 08:20:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573806024; bh=H8/ptq9B4Ies/NmvPzkI+OvZqdjM6J5mCWh0lRahEfM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oyHuM2iKsp/09b2d5wyaUZQLc8d6WwBPoQmY9afiswqW3NjXuCxwLLguhU+HxM7Lz 7R+OrG3d7kbl+0Nr8rwAMBmzugg3e9PswmUaLgKk2jnp53rdWVx7aMJN2KV+alWEV6 n/+T45YsuRSfrODJJIZeg2plzetRr6QbuI/3l+Rs= Date: Fri, 15 Nov 2019 16:20:22 +0800 From: Greg Kroah-Hartman To: Jouni =?iso-8859-1?Q?H=F6gander?= Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" , Lukas Bulwahn Subject: Re: [PATCH] drivers/base: Fix memory leak in error paths Message-ID: <20191115082022.GB55909@kroah.com> References: <20191114121840.5585-1-jouni.hogander@unikie.com> <20191115032603.GG793701@kroah.com> <878soha7tc.fsf@unikie.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <878soha7tc.fsf@unikie.com> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 15, 2019 at 09:59:43AM +0200, Jouni Högander wrote: > Greg Kroah-Hartman writes: > > > On Thu, Nov 14, 2019 at 02:18:40PM +0200, jouni.hogander@unikie.com wrote: > >> From: Jouni Hogander > >> > >> Currently error paths are using device_del to clean-up preparations > >> done by device_add. This is causing memory leak as free of dev->p > >> allocated in device_add is freed in device_release. This is fixed by > >> moving freeing dev->p to counterpart of device_add i.e. device_del. > > > > Are you sure that is safe? The device can still be "alive" after > > device_del() is called. The only place you know that it should be freed > > is in the release callback. > > Now as you pointed this out I'm not. > > > > >> This memory leak was reported by Syzkaller: > >> > >> BUG: memory leak unreferenced object 0xffff8880675ca008 (size 256): > >> comm "netdev_register", pid 281, jiffies 4294696663 (age 6.808s) > >> hex dump (first 32 bytes): > >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > >> backtrace: > >> [<0000000058ca4711>] kmem_cache_alloc_trace+0x167/0x280 > >> [<000000002340019b>] device_add+0x882/0x1750 > >> [<000000001d588c3a>] netdev_register_kobject+0x128/0x380 > >> [<0000000011ef5535>] register_netdevice+0xa1b/0xf00 > >> [<000000007fcf1c99>] __tun_chr_ioctl+0x20d5/0x3dd0 > >> [<000000006a5b7b2b>] tun_chr_ioctl+0x2f/0x40 > >> [<00000000f30f834a>] do_vfs_ioctl+0x1c7/0x1510 > >> [<00000000fba062ea>] ksys_ioctl+0x99/0xb0 > >> [<00000000b1c1b8d2>] __x64_sys_ioctl+0x78/0xb0 > >> [<00000000984cabb9>] do_syscall_64+0x16f/0x580 > >> [<000000000bde033d>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > >> [<00000000e6ca2d9f>] 0xffffffffffffffff > > > > How is this a leak? This is in device_add(), not removing the device. > > When the structure really is freed then it can be removed. > > In net/core/net-sysfs.c:netdev_register_kobject device_add allocates > dev->p. Now if register_queue_kobjects fails the error path is calling > device_del and dev->p is never freed. Proper fix here could be to call > put_device after device_del? Hm, this sounds like you have a reference count leak here, as put_device() should be properly called already in this case. You might want to look further to see where exactly the register_queue_kobjects() call fails in order to see if we grabbed a reference we forgot to put back on an error path. thanks, greg k-h