From: Wen Gu guwen@linux.alibaba.com
[ Upstream commit 20c9398d3309d170300d67643b851fd26783af24 ]
We encountered some crashes caused by the race between SMC-R link access and link clear that triggered by abnormal link group termination, such as port error.
Here is an example of this kind of crashes:
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: <TASK> ? __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 </TASK>
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) |
These crashes are similarly caused by clearing SMC-R link resources when some functions is still accessing to them. This patch tries to fix the issue by introducing reference count of SMC-R links and ensuring that the sensitive resources of links won't be cleared until reference count reaches 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 smc_conn_create() 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 guwen@linux.alibaba.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/smc/smc_core.c | 52 +++++++++++++++++++++++++++++++++++----------- net/smc/smc_core.h | 4 ++++ 2 files changed, 44 insertions(+), 12 deletions(-)
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index 84b89d13c3359..f4de45ac88189 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -745,6 +745,8 @@ 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 +996,12 @@ void smc_switch_link_and_count(struct smc_connection *conn, struct smc_link *to_lnk) { atomic_dec(&conn->lnk->conn_cnt); + /* link_hold in smc_conn_create() */ + smcr_link_put(conn->lnk); conn->lnk = to_lnk; atomic_inc(&conn->lnk->conn_cnt); + /* link_put in smc_conn_free() */ + smcr_link_hold(conn->lnk); }
struct smc_link *smc_switch_conns(struct smc_link_group *lgr, @@ -1152,6 +1158,8 @@ 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 smc_conn_create() */ smc_lgr_put(lgr); /* lgr_hold in smc_conn_create() */ }
@@ -1208,22 +1216,11 @@ static void smcr_rtoken_clear_link(struct smc_link *lnk) } }
-/* must be called under lgr->llc_conf_mutex lock */ -void smcr_link_clear(struct smc_link *lnk, bool log) +static void __smcr_link_clear(struct smc_link *lnk) { struct smc_link_group *lgr = lnk->lgr; struct smc_ib_device *smcibdev;
- if (!lgr || lnk->state == SMC_LNK_UNUSED) - return; - lnk->peer_qpn = 0; - smc_llc_link_clear(lnk, log); - smcr_buf_unmap_lgr(lnk); - smcr_rtoken_clear_link(lnk); - smc_ib_modify_qp_error(lnk); - smc_wr_free_link(lnk); - smc_ib_destroy_queue_pair(lnk); - smc_ib_dealloc_protection_domain(lnk); smc_wr_free_link_mem(lnk); smc_ibdev_cnt_dec(lnk); put_device(&lnk->smcibdev->ibdev->dev); @@ -1235,6 +1232,35 @@ void smcr_link_clear(struct smc_link *lnk, bool log) smc_lgr_put(lgr); /* lgr_hold in smcr_link_init() */ }
+/* must be called under lgr->llc_conf_mutex lock */ +void smcr_link_clear(struct smc_link *lnk, bool log) +{ + if (!lnk->lgr || lnk->clearing || + lnk->state == SMC_LNK_UNUSED) + return; + lnk->clearing = 1; + lnk->peer_qpn = 0; + smc_llc_link_clear(lnk, log); + smcr_buf_unmap_lgr(lnk); + smcr_rtoken_clear_link(lnk); + smc_ib_modify_qp_error(lnk); + smc_wr_free_link(lnk); + smc_ib_destroy_queue_pair(lnk); + smc_ib_dealloc_protection_domain(lnk); + 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, struct smc_buf_desc *buf_desc) { @@ -1872,6 +1898,8 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini) goto out; } smc_lgr_hold(conn->lgr); /* lgr_put in smc_conn_free() */ + if (!conn->lgr->is_smcd) + smcr_link_hold(conn->lnk); /* link_put in smc_conn_free() */ conn->freed = 0; conn->local_tx_ctrl.common.type = SMC_CDC_MSG_TYPE; conn->local_tx_ctrl.len = SMC_WR_TX_SIZE; diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h index 51203b16307be..e73217f52f3dd 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_core_exit(void); 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);