From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752857AbdBBSkh (ORCPT ); Thu, 2 Feb 2017 13:40:37 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:49612 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751634AbdBBSkd (ORCPT ); Thu, 2 Feb 2017 13:40:33 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Robert Shearman , "David S. Miller" Subject: [PATCH 4.9 31/51] lwtunnel: Fix oops on state free after encap module unload Date: Thu, 2 Feb 2017 19:37:50 +0100 Message-Id: <20170202183346.731065159@linuxfoundation.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170202183345.067336143@linuxfoundation.org> References: <20170202183345.067336143@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Robert Shearman [ Upstream commit 85c814016ce3b371016c2c054a905fa2492f5a65 ] When attempting to free lwtunnel state after the module for the encap has been unloaded an oops occurs: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 IP: lwtstate_free+0x18/0x40 [..] task: ffff88003e372380 task.stack: ffffc900001fc000 RIP: 0010:lwtstate_free+0x18/0x40 RSP: 0018:ffff88003fd83e88 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff88002bbb3380 RCX: ffff88000c91a300 [..] Call Trace: free_fib_info_rcu+0x195/0x1a0 ? rt_fibinfo_free+0x50/0x50 rcu_process_callbacks+0x2d3/0x850 ? rcu_process_callbacks+0x296/0x850 __do_softirq+0xe4/0x4cb irq_exit+0xb0/0xc0 smp_apic_timer_interrupt+0x3d/0x50 apic_timer_interrupt+0x93/0xa0 [..] Code: e8 6e c6 fc ff 89 d8 5b 5d c3 bb de ff ff ff eb f4 66 90 66 66 66 66 90 55 48 89 e5 53 0f b7 07 48 89 fb 48 8b 04 c5 00 81 d5 81 <48> 8b 40 08 48 85 c0 74 13 ff d0 48 8d 7b 20 be 20 00 00 00 e8 The problem is after the module for the encap can be unloaded the corresponding ops is removed and is thus NULL here. Modules implementing lwtunnel ops should not be allowed to unload while there is state alive using those ops, so grab the module reference for the ops on creating lwtunnel state and of course release the reference when freeing the state. Fixes: 1104d9ba443a ("lwtunnel: Add destroy state operation") Signed-off-by: Robert Shearman Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/net/lwtunnel.h | 5 +---- net/core/lwtunnel.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 5 deletions(-) --- a/include/net/lwtunnel.h +++ b/include/net/lwtunnel.h @@ -48,10 +48,7 @@ struct lwtunnel_encap_ops { }; #ifdef CONFIG_LWTUNNEL -static inline void lwtstate_free(struct lwtunnel_state *lws) -{ - kfree(lws); -} +void lwtstate_free(struct lwtunnel_state *lws); static inline struct lwtunnel_state * lwtstate_get(struct lwtunnel_state *lws) --- a/net/core/lwtunnel.c +++ b/net/core/lwtunnel.c @@ -66,6 +66,15 @@ EXPORT_SYMBOL(lwtunnel_state_alloc); static const struct lwtunnel_encap_ops __rcu * lwtun_encaps[LWTUNNEL_ENCAP_MAX + 1] __read_mostly; +void lwtstate_free(struct lwtunnel_state *lws) +{ + const struct lwtunnel_encap_ops *ops = lwtun_encaps[lws->type]; + + kfree(lws); + module_put(ops->owner); +} +EXPORT_SYMBOL(lwtstate_free); + int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *ops, unsigned int num) { @@ -111,8 +120,11 @@ int lwtunnel_build_state(struct net_devi ret = -EOPNOTSUPP; rcu_read_lock(); ops = rcu_dereference(lwtun_encaps[encap_type]); - if (likely(ops && ops->build_state)) + if (likely(ops && ops->build_state && try_module_get(ops->owner))) { ret = ops->build_state(dev, encap, family, cfg, lws); + if (ret) + module_put(ops->owner); + } rcu_read_unlock(); return ret;