From patchwork Tue Dec 28 09:20:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wen Gu X-Patchwork-Id: 12700243 X-Patchwork-Delegate: kuba@kernel.org 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 B421CC433EF for ; Tue, 28 Dec 2021 09:20:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235877AbhL1JUz (ORCPT ); Tue, 28 Dec 2021 04:20:55 -0500 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:41333 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233106AbhL1JUx (ORCPT ); Tue, 28 Dec 2021 04:20:53 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=guwen@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0V057EhM_1640683240; Received: from e02h04404.eu6sqa(mailfrom:guwen@linux.alibaba.com fp:SMTPD_---0V057EhM_1640683240) by smtp.aliyun-inc.com(127.0.0.1); Tue, 28 Dec 2021 17:20:51 +0800 From: Wen Gu To: kgraul@linux.ibm.com, davem@davemloft.net, kuba@kernel.org Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dust.li@linux.alibaba.com, tonylu@linux.alibaba.com Subject: [RFC PATCH net 1/2] net/smc: Resolve the race between link group access and termination Date: Tue, 28 Dec 2021 17:20:39 +0800 Message-Id: <1640683240-62472-2-git-send-email-guwen@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1640683240-62472-1-git-send-email-guwen@linux.alibaba.com> References: <1640683240-62472-1-git-send-email-guwen@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC We encountered some crashes caused by the race between the access and the termination of link groups. Here are some of panic stacks we met: 1) Race between smc_clc_wait_msg() and __smc_lgr_terminate() BUG: kernel NULL pointer dereference, address: 00000000000002f0 Workqueue: smc_hs_wq smc_listen_work [smc] RIP: 0010:smc_clc_wait_msg+0x3eb/0x5c0 [smc] Call Trace: ? smc_clc_send_accept+0x45/0xa0 [smc] ? smc_clc_send_accept+0x45/0xa0 [smc] smc_listen_work+0x783/0x1220 [smc] ? finish_task_switch+0xc4/0x2e0 ? process_one_work+0x1ad/0x3c0 process_one_work+0x1ad/0x3c0 worker_thread+0x4c/0x390 ? rescuer_thread+0x320/0x320 kthread+0x149/0x190 ? set_kthread_struct+0x40/0x40 ret_from_fork+0x1f/0x30 smc_listen_work() abnormal case like port error --------------------------------------------------------------- | __smc_lgr_terminate() | |- smc_conn_kill() | |- smc_lgr_unregister_conn() | |- set conn->lgr = NULL smc_clc_wait_msg() | |- access conn->lgr (panic) | 2) Race between smc_setsockopt() and __smc_lgr_terminate() BUG: kernel NULL pointer dereference, address: 00000000000002e8 RIP: 0010:smc_setsockopt+0x17a/0x280 [smc] Call Trace: __sys_setsockopt+0xfc/0x190 __x64_sys_setsockopt+0x20/0x30 do_syscall_64+0x34/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae smc_setsockopt() abnormal case like port error -------------------------------------------------------------- | __smc_lgr_terminate() | |- smc_conn_kill() | |- smc_lgr_unregister_conn() | |- set conn->lgr = NULL mod_delayed_work() | |- access conn->lgr (panic) | There are some other panic points and they are caused by the simmilar reason as described above, which is accessing link group after termination, thus getting a NULL pointer or invalid resource. Currently, there seems to be no synchronization between the link group access and a sudden termination of it. This patch tries to fix this by introducing reference count of link group and not freeing link group until reference count is zero. Link group might be referred to by link or smc connection. So the operation to the link group reference count can be concluded as follows: object [hold or initialized as 1] [put] -------------------------------------------------------------------- link group smc_lgr_create() smc_lgr_free() connections smc_lgr_register_conn() smc_conn_free() links smcr_link_init() smcr_link_clear() Througth this way, we extend the life cycle of link group and ensure it is longer than the life cycle of connections and links above it, so that avoid invalid access to link group after its termination. Signed-off-by: Wen Gu --- net/smc/smc.h | 1 + net/smc/smc_core.c | 45 ++++++++++++++++++++++++++++++++++++++++----- net/smc/smc_core.h | 3 +++ 3 files changed, 44 insertions(+), 5 deletions(-) diff --git a/net/smc/smc.h b/net/smc/smc.h index 1a4fc1c..3d0b8e3 100644 --- a/net/smc/smc.h +++ b/net/smc/smc.h @@ -221,6 +221,7 @@ struct smc_connection { */ u64 peer_token; /* SMC-D token of peer */ u8 killed : 1; /* abnormal termination */ + u8 freed : 1; /* normal termiation */ u8 out_of_sync : 1; /* out of sync with peer */ }; diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index 1f40b8e..d72eb13 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -184,6 +184,7 @@ static int smc_lgr_register_conn(struct smc_connection *conn, bool first) conn->alert_token_local = 0; } smc_lgr_add_alert_token(conn); + smc_lgr_hold(conn->lgr); /* lgr_put in smc_conn_free() */ conn->lgr->conns_num++; return 0; } @@ -216,7 +217,6 @@ static void smc_lgr_unregister_conn(struct smc_connection *conn) __smc_lgr_unregister_conn(conn); } write_unlock_bh(&lgr->conns_lock); - conn->lgr = NULL; } int smc_nl_get_sys_info(struct sk_buff *skb, struct netlink_callback *cb) @@ -749,6 +749,7 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk, lnk->path_mtu = lnk->smcibdev->pattr[lnk->ibport - 1].active_mtu; lnk->link_id = smcr_next_link_id(lgr); lnk->lgr = lgr; + smc_lgr_hold(lgr); /* lgr_put in smcr_link_clear() */ lnk->link_idx = link_idx; smc_ibdev_cnt_inc(lnk); smcr_copy_dev_info_to_link(lnk); @@ -841,6 +842,7 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini) lgr->terminating = 0; lgr->freeing = 0; lgr->vlan_id = ini->vlan_id; + refcount_set(&lgr->refcnt, 1); /* set lgr refcnt to 1 */ mutex_init(&lgr->sndbufs_lock); mutex_init(&lgr->rmbs_lock); rwlock_init(&lgr->conns_lock); @@ -1120,8 +1122,20 @@ void smc_conn_free(struct smc_connection *conn) { struct smc_link_group *lgr = conn->lgr; - if (!lgr) + if (!lgr || conn->freed) + /* smc connection wasn't registered to a link group + * or has already been freed before. + * + * Judge these to ensure that lgr refcnt will be put + * only once if connection has been registered to a + * link group successfully. + */ return; + + conn->freed = 1; + if (conn->killed) + goto lgr_put; + if (lgr->is_smcd) { if (!list_empty(&lgr->list)) smc_ism_unset_conn(conn); @@ -1138,6 +1152,8 @@ void smc_conn_free(struct smc_connection *conn) if (!lgr->conns_num) smc_lgr_schedule_free_work(lgr); +lgr_put: + smc_lgr_put(lgr); /* lgr_hold in smc_lgr_register_conn() */ } /* unregister a link from a buf_desc */ @@ -1209,6 +1225,7 @@ void smcr_link_clear(struct smc_link *lnk, bool log) smc_ib_destroy_queue_pair(lnk); smc_ib_dealloc_protection_domain(lnk); smc_wr_free_link_mem(lnk); + smc_lgr_put(lnk->lgr); /* lgr_hold in smcr_link_init() */ smc_ibdev_cnt_dec(lnk); put_device(&lnk->smcibdev->ibdev->dev); smcibdev = lnk->smcibdev; @@ -1283,6 +1300,15 @@ static void smc_lgr_free_bufs(struct smc_link_group *lgr) __smc_lgr_free_bufs(lgr, true); } +/* won't be freed until no one accesses to lgr anymore */ +static void __smc_lgr_free(struct smc_link_group *lgr) +{ + smc_lgr_free_bufs(lgr); + if (!lgr->is_smcd) + smc_wr_free_lgr_mem(lgr); + kfree(lgr); +} + /* remove a link group */ static void smc_lgr_free(struct smc_link_group *lgr) { @@ -1298,7 +1324,6 @@ static void smc_lgr_free(struct smc_link_group *lgr) smc_llc_lgr_clear(lgr); } - smc_lgr_free_bufs(lgr); destroy_workqueue(lgr->tx_wq); if (lgr->is_smcd) { smc_ism_put_vlan(lgr->smcd, lgr->vlan_id); @@ -1306,11 +1331,21 @@ static void smc_lgr_free(struct smc_link_group *lgr) if (!atomic_dec_return(&lgr->smcd->lgr_cnt)) wake_up(&lgr->smcd->lgrs_deleted); } else { - smc_wr_free_lgr_mem(lgr); if (!atomic_dec_return(&lgr_cnt)) wake_up(&lgrs_deleted); } - kfree(lgr); + smc_lgr_put(lgr); /* theoretically last lgr_put */ +} + +void smc_lgr_hold(struct smc_link_group *lgr) +{ + refcount_inc(&lgr->refcnt); +} + +void smc_lgr_put(struct smc_link_group *lgr) +{ + if (refcount_dec_and_test(&lgr->refcnt)) + __smc_lgr_free(lgr); } static void smc_sk_wake_ups(struct smc_sock *smc) diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h index d63b082..51203b1 100644 --- a/net/smc/smc_core.h +++ b/net/smc/smc_core.h @@ -249,6 +249,7 @@ struct smc_link_group { u8 terminating : 1;/* lgr is terminating */ u8 freeing : 1; /* lgr is being freed */ + refcount_t refcnt; /* lgr reference count */ bool is_smcd; /* SMC-R or SMC-D */ u8 smc_version; u8 negotiated_eid[SMC_MAX_EID_LEN]; @@ -470,6 +471,8 @@ static inline void smc_set_pci_values(struct pci_dev *pci_dev, void smc_lgr_cleanup_early(struct smc_connection *conn); void smc_lgr_terminate_sched(struct smc_link_group *lgr); +void smc_lgr_hold(struct smc_link_group *lgr); +void smc_lgr_put(struct smc_link_group *lgr); void smcr_port_add(struct smc_ib_device *smcibdev, u8 ibport); void smcr_port_err(struct smc_ib_device *smcibdev, u8 ibport); void smc_smcd_terminate(struct smcd_dev *dev, u64 peer_gid, From patchwork Tue Dec 28 09:20:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wen Gu X-Patchwork-Id: 12700244 X-Patchwork-Delegate: kuba@kernel.org 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 E2AE4C433FE for ; Tue, 28 Dec 2021 09:21:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235882AbhL1JU4 (ORCPT ); Tue, 28 Dec 2021 04:20:56 -0500 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:51423 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233108AbhL1JUy (ORCPT ); Tue, 28 Dec 2021 04:20:54 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R651e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=guwen@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0V057EhM_1640683240; Received: from e02h04404.eu6sqa(mailfrom:guwen@linux.alibaba.com fp:SMTPD_---0V057EhM_1640683240) by smtp.aliyun-inc.com(127.0.0.1); Tue, 28 Dec 2021 17:20:52 +0800 From: Wen Gu To: kgraul@linux.ibm.com, davem@davemloft.net, kuba@kernel.org Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dust.li@linux.alibaba.com, tonylu@linux.alibaba.com Subject: [RFC PATCH net 2/2] net/smc: Resolve the race between SMC-R link access and clear Date: Tue, 28 Dec 2021 17:20:40 +0800 Message-Id: <1640683240-62472-3-git-send-email-guwen@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1640683240-62472-1-git-send-email-guwen@linux.alibaba.com> References: <1640683240-62472-1-git-send-email-guwen@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC We encountered some crashes caused by the race between SMC-R link access and link clear triggered by link group termination in abnormal case, like port error. Here are some of panic stacks we met: 1) Race between smc_llc_flow_initiate() and smcr_link_clear() BUG: kernel NULL pointer dereference, address: 0000000000000000 Workqueue: smc_hs_wq smc_listen_work [smc] RIP: 0010:smc_llc_flow_initiate+0x44/0x190 [smc] Call Trace: ? __smc_buf_create+0x75a/0x950 [smc] smcr_lgr_reg_rmbs+0x2a/0xbf [smc] smc_listen_work+0xf72/0x1230 [smc] ? process_one_work+0x25c/0x600 process_one_work+0x25c/0x600 worker_thread+0x4f/0x3a0 ? process_one_work+0x600/0x600 kthread+0x15d/0x1a0 ? set_kthread_struct+0x40/0x40 ret_from_fork+0x1f/0x30 smc_listen_work() __smc_lgr_terminate() --------------------------------------------------------------- | smc_lgr_free() | |- smcr_link_clear() | |- memset(lnk, 0) smc_listen_rdma_reg() | |- smcr_lgr_reg_rmbs() | |- smc_llc_flow_initiate() | |- access lnk->lgr (panic) | 2) Race between smc_wr_tx_dismiss_slots() and smcr_link_clear() BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:_find_first_bit+0x8/0x50 Call Trace: smc_wr_tx_dismiss_slots+0x34/0xc0 [smc] ? smc_cdc_tx_filter+0x10/0x10 [smc] smc_conn_free+0xd8/0x100 [smc] __smc_release+0xf1/0x140 [smc] smc_release+0x89/0x1b0 [smc] __sock_release+0x37/0xb0 sock_close+0x14/0x20 __fput+0xa9/0x260 task_work_run+0x6b/0xb0 do_exit+0x3ef/0xd40 do_group_exit+0x47/0xb0 __x64_sys_exit_group+0x14/0x20 do_syscall_64+0x34/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae smc_conn_free() __smc_lgr_terminate() ---------------------------------------------------------------- | smc_lgr_free() | |- smcr_link_clear() | |- smc_wr_free_link_mem() | |- lnk->wr_tx_mask = NULL; smc_wr_tx_dismiss_slots() | |- for_each_set_bit(link->wr_tx_mask) | |- (panic) | These crashes are caused by clearing SMC-R link resources when someone is still accessing to them. So this patch tries to fix it by introducing reference count of SMC-R links and ensuring that the sensitive resources of links are not cleared until reference count is zero. The operation to the SMC-R link reference count can be concluded as follows: object [hold or initialized as 1] [put] -------------------------------------------------------------------- links smcr_link_init() smcr_link_clear() connections smcr_lgr_conn_assign_link() smc_conn_free() Through this way, the clear of SMC-R links is later than the free of all the smc connections above it, thus avoiding the unsafe reference to SMC-R links. Signed-off-by: Wen Gu --- net/smc/smc_core.c | 43 +++++++++++++++++++++++++++++++++++-------- net/smc/smc_core.h | 4 ++++ 2 files changed, 39 insertions(+), 8 deletions(-) diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index d72eb13..83a80e6 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -155,6 +155,7 @@ static int smcr_lgr_conn_assign_link(struct smc_connection *conn, bool first) if (!conn->lnk) return SMC_CLC_DECL_NOACTLINK; atomic_inc(&conn->lnk->conn_cnt); + smcr_link_hold(conn->lnk); /* link_put in smc_conn_free() */ return 0; } @@ -746,6 +747,8 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk, } get_device(&lnk->smcibdev->ibdev->dev); atomic_inc(&lnk->smcibdev->lnk_cnt); + refcount_set(&lnk->refcnt, 1); /* link refcnt is set to 1 */ + lnk->clearing = 0; lnk->path_mtu = lnk->smcibdev->pattr[lnk->ibport - 1].active_mtu; lnk->link_id = smcr_next_link_id(lgr); lnk->lgr = lgr; @@ -994,8 +997,12 @@ void smc_switch_link_and_count(struct smc_connection *conn, struct smc_link *to_lnk) { atomic_dec(&conn->lnk->conn_cnt); + /* put old link, hold in smcr_lgr_conn_assign_link() */ + smcr_link_put(conn->lnk); conn->lnk = to_lnk; atomic_inc(&conn->lnk->conn_cnt); + /* hold new link, put in smc_conn_free() */ + smcr_link_hold(conn->lnk); } struct smc_link *smc_switch_conns(struct smc_link_group *lgr, @@ -1126,9 +1133,9 @@ void smc_conn_free(struct smc_connection *conn) /* smc connection wasn't registered to a link group * or has already been freed before. * - * Judge these to ensure that lgr refcnt will be put - * only once if connection has been registered to a - * link group successfully. + * Judge these to ensure that lgr/link refcnt will be + * put only once if connection has been registered to + * a link group successfully. */ return; @@ -1153,6 +1160,8 @@ void smc_conn_free(struct smc_connection *conn) if (!lgr->conns_num) smc_lgr_schedule_free_work(lgr); lgr_put: + if (!lgr->is_smcd) + smcr_link_put(conn->lnk); /* link_hold in smcr_lgr_conn_assign_link() */ smc_lgr_put(lgr); /* lgr_hold in smc_lgr_register_conn() */ } @@ -1209,13 +1218,23 @@ static void smcr_rtoken_clear_link(struct smc_link *lnk) } } +void __smcr_link_clear(struct smc_link *lnk) +{ + smc_wr_free_link_mem(lnk); + smc_lgr_put(lnk->lgr); /* lgr_hold in smcr_link_init() */ + memset(lnk, 0, sizeof(struct smc_link)); + lnk->state = SMC_LNK_UNUSED; +} + /* must be called under lgr->llc_conf_mutex lock */ void smcr_link_clear(struct smc_link *lnk, bool log) { struct smc_ib_device *smcibdev; - if (!lnk->lgr || lnk->state == SMC_LNK_UNUSED) + if (lnk->clearing || !lnk->lgr || + lnk->state == SMC_LNK_UNUSED) return; + lnk->clearing = 1; lnk->peer_qpn = 0; smc_llc_link_clear(lnk, log); smcr_buf_unmap_lgr(lnk); @@ -1224,15 +1243,23 @@ void smcr_link_clear(struct smc_link *lnk, bool log) smc_wr_free_link(lnk); smc_ib_destroy_queue_pair(lnk); smc_ib_dealloc_protection_domain(lnk); - smc_wr_free_link_mem(lnk); - smc_lgr_put(lnk->lgr); /* lgr_hold in smcr_link_init() */ smc_ibdev_cnt_dec(lnk); put_device(&lnk->smcibdev->ibdev->dev); smcibdev = lnk->smcibdev; - memset(lnk, 0, sizeof(struct smc_link)); - lnk->state = SMC_LNK_UNUSED; if (!atomic_dec_return(&smcibdev->lnk_cnt)) wake_up(&smcibdev->lnks_deleted); + smcr_link_put(lnk); /* theoretically last link_put */ +} + +void smcr_link_hold(struct smc_link *lnk) +{ + refcount_inc(&lnk->refcnt); +} + +void smcr_link_put(struct smc_link *lnk) +{ + if (refcount_dec_and_test(&lnk->refcnt)) + __smcr_link_clear(lnk); } static void smcr_buf_free(struct smc_link_group *lgr, bool is_rmb, diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h index 51203b1..e73217f 100644 --- a/net/smc/smc_core.h +++ b/net/smc/smc_core.h @@ -137,6 +137,8 @@ struct smc_link { u8 peer_link_uid[SMC_LGR_ID_SIZE]; /* peer uid */ u8 link_idx; /* index in lgr link array */ u8 link_is_asym; /* is link asymmetric? */ + u8 clearing : 1; /* link is being cleared */ + refcount_t refcnt; /* link reference count */ struct smc_link_group *lgr; /* parent link group */ struct work_struct link_down_wrk; /* wrk to bring link down */ char ibname[IB_DEVICE_NAME_MAX]; /* ib device name */ @@ -504,6 +506,8 @@ void smc_rtoken_set2(struct smc_link_group *lgr, int rtok_idx, int link_id, int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk, u8 link_idx, struct smc_init_info *ini); void smcr_link_clear(struct smc_link *lnk, bool log); +void smcr_link_hold(struct smc_link *lnk); +void smcr_link_put(struct smc_link *lnk); void smc_switch_link_and_count(struct smc_connection *conn, struct smc_link *to_lnk); int smcr_buf_map_lgr(struct smc_link *lnk);