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Date: Thu, 1 Sep 2022 14:45:36 +0200
From: Wenjia Zhang <wenjia@...ux.ibm.com>
To: liuyacan@...p.netease.com
Cc: davem@...emloft.net, edumazet@...gle.com, kgraul@...ux.ibm.com,
kuba@...nel.org, linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org, netdev@...r.kernel.org,
pabeni@...hat.com, tonylu@...ux.alibaba.com,
ubraun@...ux.vnet.ibm.com, wintera@...ux.ibm.com,
alibuda@...ux.alibaba.com
Subject: Re: [PATCH net v4] net/smc: Fix possible access to freed memory in
link clear
On 01.09.22 14:26, liuyacan@...p.netease.com wrote:
>>> From: Yacan Liu <liuyacan@...p.netease.com>
>>>
>>> After modifying the QP to the Error state, all RX WR would be completed
>>> with WC in IB_WC_WR_FLUSH_ERR status. Current implementation does not
>>> wait for it is done, but destroy the QP and free the link group directly.
>>> So there is a risk that accessing the freed memory in tasklet context.
>>>
>>> Here is a crash example:
>>>
>>> BUG: unable to handle page fault for address: ffffffff8f220860
>>> #PF: supervisor write access in kernel mode
>>> #PF: error_code(0x0002) - not-present page
>>> PGD f7300e067 P4D f7300e067 PUD f7300f063 PMD 8c4e45063 PTE 800ffff08c9df060
>>> Oops: 0002 [#1] SMP PTI
>>> CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: G S OE 5.10.0-0607+ #23
>>> Hardware name: Inspur NF5280M4/YZMB-00689-101, BIOS 4.1.20 07/09/2018
>>> RIP: 0010:native_queued_spin_lock_slowpath+0x176/0x1b0
>>> Code: f3 90 48 8b 32 48 85 f6 74 f6 eb d5 c1 ee 12 83 e0 03 83 ee 01 48 c1 e0 05 48 63 f6 48 05 00 c8 02 00 48 03 04 f5 00 09 98 8e <48> 89 10 8b 42 08 85 c0 75 09 f3 90 8b 42 08 85 c0 74 f7 48 8b 32
>>> RSP: 0018:ffffb3b6c001ebd8 EFLAGS: 00010086
>>> RAX: ffffffff8f220860 RBX: 0000000000000246 RCX: 0000000000080000
>>> RDX: ffff91db1f86c800 RSI: 000000000000173c RDI: ffff91db62bace00
>>> RBP: ffff91db62bacc00 R08: 0000000000000000 R09: c00000010000028b
>>> R10: 0000000000055198 R11: ffffb3b6c001ea58 R12: ffff91db80e05010
>>> R13: 000000000000000a R14: 0000000000000006 R15: 0000000000000040
>>> FS: 0000000000000000(0000) GS:ffff91db1f840000(0000) knlGS:0000000000000000
>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: ffffffff8f220860 CR3: 00000001f9580004 CR4: 00000000003706e0
>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>> Call Trace:
>>> <IRQ>
>>> _raw_spin_lock_irqsave+0x30/0x40
>>> mlx5_ib_poll_cq+0x4c/0xc50 [mlx5_ib]
>>> smc_wr_rx_tasklet_fn+0x56/0xa0 [smc]
>>> tasklet_action_common.isra.21+0x66/0x100
>>> __do_softirq+0xd5/0x29c
>>> asm_call_irq_on_stack+0x12/0x20
>>> </IRQ>
>>> do_softirq_own_stack+0x37/0x40
>>> irq_exit_rcu+0x9d/0xa0
>>> sysvec_call_function_single+0x34/0x80
>>> asm_sysvec_call_function_single+0x12/0x20
>>>
>>> Fixes: bd4ad57718cc ("smc: initialize IB transport incl. PD, MR, QP, CQ, event, WR")
>>> Signed-off-by: Yacan Liu <liuyacan@...p.netease.com>
>>>
>>> ---
>>> Chagen in v4:
>>> -- Remove the rx_drain flag because smc_wr_rx_post() may not have been called.
>>> -- Remove timeout.
>>> Change in v3:
>>> -- Tune commit message (Signed-Off tag, Fixes tag).
>>> Tune code to avoid column length exceeding.
>>> Change in v2:
>>> -- Fix some compile warnings and errors.
>>> ---
>>> net/smc/smc_core.c | 2 ++
>>> net/smc/smc_core.h | 2 ++
>>> net/smc/smc_wr.c | 9 +++++++++
>>> net/smc/smc_wr.h | 1 +
>>> 4 files changed, 14 insertions(+)
>>>
>>> diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
>>> index ff49a11f5..f92a916e9 100644
>>> --- a/net/smc/smc_core.c
>>> +++ b/net/smc/smc_core.c
>>> @@ -757,6 +757,7 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk,
>>> lnk->lgr = lgr;
>>> smc_lgr_hold(lgr); /* lgr_put in smcr_link_clear() */
>>> lnk->link_idx = link_idx;
>>> + lnk->wr_rx_id_compl = 0;
>>> smc_ibdev_cnt_inc(lnk);
>>> smcr_copy_dev_info_to_link(lnk);
>>> atomic_set(&lnk->conn_cnt, 0);
>>> @@ -1269,6 +1270,7 @@ void smcr_link_clear(struct smc_link *lnk, bool log)
>>> smcr_buf_unmap_lgr(lnk);
>>> smcr_rtoken_clear_link(lnk);
>>> smc_ib_modify_qp_error(lnk);
>>> + smc_wr_drain_cq(lnk);
>>> smc_wr_free_link(lnk);
>>> smc_ib_destroy_queue_pair(lnk);
>>> smc_ib_dealloc_protection_domain(lnk);
>>> diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
>>> index fe8b524ad..285f9bd8e 100644
>>> --- a/net/smc/smc_core.h
>>> +++ b/net/smc/smc_core.h
>>> @@ -115,8 +115,10 @@ struct smc_link {
>>> dma_addr_t wr_rx_dma_addr; /* DMA address of wr_rx_bufs */
>>> dma_addr_t wr_rx_v2_dma_addr; /* DMA address of v2 rx buf*/
>>> u64 wr_rx_id; /* seq # of last recv WR */
>>> + u64 wr_rx_id_compl; /* seq # of last completed WR */
>>> u32 wr_rx_cnt; /* number of WR recv buffers */
>>> unsigned long wr_rx_tstamp; /* jiffies when last buf rx */
>>> + wait_queue_head_t wr_rx_empty_wait; /* wait for RQ empty */
>>>
>>> struct ib_reg_wr wr_reg; /* WR register memory region */
>>> wait_queue_head_t wr_reg_wait; /* wait for wr_reg result */
>>> diff --git a/net/smc/smc_wr.c b/net/smc/smc_wr.c
>>> index 26f8f240d..bc8793803 100644
>>> --- a/net/smc/smc_wr.c
>>> +++ b/net/smc/smc_wr.c
>>> @@ -454,6 +454,7 @@ static inline void smc_wr_rx_process_cqes(struct ib_wc wc[], int num)
>>>
>>> for (i = 0; i < num; i++) {
>>> link = wc[i].qp->qp_context;
>>> + link->wr_rx_id_compl = wc[i].wr_id;
>>> if (wc[i].status == IB_WC_SUCCESS) {
>>> link->wr_rx_tstamp = jiffies;
>>> smc_wr_rx_demultiplex(&wc[i]);
>>> @@ -465,6 +466,8 @@ static inline void smc_wr_rx_process_cqes(struct ib_wc wc[], int num)
>>> case IB_WC_RNR_RETRY_EXC_ERR:
>>> case IB_WC_WR_FLUSH_ERR:
>>> smcr_link_down_cond_sched(link);
>>> + if (link->wr_rx_id_compl == link->wr_rx_id)
>>> + wake_up(&link->wr_rx_empty_wait);
>>> break;
>>> default:
>>> smc_wr_rx_post(link); /* refill WR RX */
>>> @@ -631,6 +634,11 @@ static void smc_wr_init_sge(struct smc_link *lnk)
>>> lnk->wr_reg.access = IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_WRITE;
>>> }
>>>
>>> +void smc_wr_drain_cq(struct smc_link *lnk)
>>> +{
>>> + wait_event(lnk->wr_rx_empty_wait, lnk->wr_rx_id_compl == lnk->wr_rx_id);
>>> +}
>>> +
>>> void smc_wr_free_link(struct smc_link *lnk)
>>> {
>>> struct ib_device *ibdev;
>>> @@ -889,6 +897,7 @@ int smc_wr_create_link(struct smc_link *lnk)
>>> atomic_set(&lnk->wr_tx_refcnt, 0);
>>> init_waitqueue_head(&lnk->wr_reg_wait);
>>> atomic_set(&lnk->wr_reg_refcnt, 0);
>>> + init_waitqueue_head(&lnk->wr_rx_empty_wait);
>>> return rc;
>>>
>>> dma_unmap:
>>> diff --git a/net/smc/smc_wr.h b/net/smc/smc_wr.h
>>> index a54e90a11..5ca5086ae 100644
>>> --- a/net/smc/smc_wr.h
>>> +++ b/net/smc/smc_wr.h
>>> @@ -101,6 +101,7 @@ static inline int smc_wr_rx_post(struct smc_link *link)
>>> int smc_wr_create_link(struct smc_link *lnk);
>>> int smc_wr_alloc_link_mem(struct smc_link *lnk);
>>> int smc_wr_alloc_lgr_mem(struct smc_link_group *lgr);
>>> +void smc_wr_drain_cq(struct smc_link *lnk);
>>> void smc_wr_free_link(struct smc_link *lnk);
>>> void smc_wr_free_link_mem(struct smc_link *lnk);
>>> void smc_wr_free_lgr_mem(struct smc_link_group *lgr);
>>
>> Thank you @Yacan for the effort to improve our code! And Thank you @Tony
>> for such valuable suggestions and testing!
>> I like the modification of this version. However, this is not a fix
>> patch to upstream, since the patches "[PATCH net-next v2 00/10] optimize
>> the parallelism of SMC-R connections" are still not applied. My
>> sugguestions:
>> - Please talk to the author (D. Wythe <alibuda@...ux.alibaba.com>) of
>> those patches I mentioned above, and ask if he can take your patch as a
>> part of the patch serie
>> - Fix patches should go to net-next
>> - Please send always send your new version separately, rather than as
>> reply to your previous version. That makes people confused.
>
> @Wenjia, Thanks a lot for your suggestions and guidance !
>
> @D. Wythe, Can you include this patch in your series of patches if it is
> convenient?
>
> Regards,
> Yacan
>
One point I was confused, fixes should goto net, sorry!
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