| Message ID | 1641265187-108970-1-git-send-email-guwen@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2] net/smc: Reset conn->lgr when link group registration fails | expand |
On 04/01/2022 03:59, Wen Gu wrote: > SMC connections might fail to be registered to a link group due to > things like unable to find a link to assign to in its creation. As > a result, connection creation will return a failure and most > resources related to the connection won't be applied or initialized, > such as conn->abort_work or conn->lnk. Patch looks good to me, but one more thing to think about: Would it be better to invoke __smc_lgr_terminate() instead of smc_lgr_schedule_free_work() when a link group was created but cannot be used now? This would immediately free up all allocated resources for this unusable link group instead of starting the default 10-minute timer until the link group is freed. __smc_lgr_terminate() takes care of completely removing the link group in the context of its caller. It is also used from within smc_lgr_cleanup_early() that is used when the very first connection of a link group is aborted.
Thanks for your reply. On 2022/1/4 5:58 pm, Karsten Graul wrote: > On 04/01/2022 03:59, Wen Gu wrote: >> SMC connections might fail to be registered to a link group due to >> things like unable to find a link to assign to in its creation. As >> a result, connection creation will return a failure and most >> resources related to the connection won't be applied or initialized, >> such as conn->abort_work or conn->lnk. > > Patch looks good to me, but one more thing to think about: > > Would it be better to invoke __smc_lgr_terminate() instead of smc_lgr_schedule_free_work() > when a link group was created but cannot be used now? This would immediately free up all > allocated resources for this unusable link group instead of starting the default 10-minute > timer until the link group is freed. > __smc_lgr_terminate() takes care of completely removing the link group in the context of > its caller. It is also used from within smc_lgr_cleanup_early() that is used when the very > first connection of a link group is aborted. Thanks for your suggestion. I also agree with using link group termination function for a immediate free. I will improve it and send a v3 patch. Thanks, Wen Gu
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index 412bc85..8edc43a 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -171,8 +171,10 @@ static int smc_lgr_register_conn(struct smc_connection *conn, bool first) if (!conn->lgr->is_smcd) { rc = smcr_lgr_conn_assign_link(conn, first); - if (rc) + if (rc) { + conn->lgr = NULL; return rc; + } } /* find a new alert_token_local value not yet used by some connection * in this link group @@ -1835,8 +1837,10 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini) write_lock_bh(&lgr->conns_lock); rc = smc_lgr_register_conn(conn, true); write_unlock_bh(&lgr->conns_lock); - if (rc) + if (rc) { + smc_lgr_schedule_free_work(lgr); goto out; + } } conn->local_tx_ctrl.common.type = SMC_CDC_MSG_TYPE; conn->local_tx_ctrl.len = SMC_WR_TX_SIZE;
SMC connections might fail to be registered to a link group due to things like unable to find a link to assign to in its creation. As a result, connection creation will return a failure and most resources related to the connection won't be applied or initialized, such as conn->abort_work or conn->lnk. If smc_conn_free() is invoked later, it will try to access the resources related to the connection, which wasn't initialized, thus causing a panic. Here is an example, a SMC-R connection failed to be registered to a link group and conn->lnk is NULL. The following crash will happen if smc_conn_free() tries to access conn->lnk in smc_cdc_tx_dismiss_slots(). BUG: kernel NULL pointer dereference, address: 0000000000000168 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 4 PID: 68 Comm: kworker/4:1 Kdump: loaded Tainted: G E 5.16.0-rc5+ #52 Workqueue: smc_hs_wq smc_listen_work [smc] RIP: 0010:smc_wr_tx_dismiss_slots+0x1e/0xc0 [smc] Call Trace: <TASK> smc_conn_free+0xd8/0x100 [smc] smc_lgr_cleanup_early+0x15/0x90 [smc] smc_listen_work+0x302/0x1230 [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> This patch tries to fix this by resetting conn->lgr to NULL if an abnormal exit occurs in smc_lgr_register_conn(), thus avoiding the crash caused by accessing the uninitialized resources in smc_conn_free(), and scheduling the link group's free work if it is new created. Fixes: 56bc3b2094b4 ("net/smc: assign link to a new connection") Signed-off-by: Wen Gu <guwen@linux.alibaba.com> --- net/smc/smc_core.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)