Re: [PATCH for-next 3/3] RDMA/rtrs: Avoid use-after-free in rtrs_clt_rdma_cm_handler

[Zhijian Li (Fujitsu)]

On 10/04/2023 21:13, Guoqing Jiang wrote:
> 
> 
> On 4/10/23 14:43, Li Zhijian wrote:
>> Currently, con will be destroyed when wait_event_interruptible_timeout()
>> returns ERESTARTSYS. But the in-flight event handler
>> rtrs_clt_rdma_cm_handler() could be rescheduled/wakeup which
>> may cause a use-after-free.
>>
>>      WARNING: CPU: 0 PID: 14766 at drivers/infiniband/ulp/rtrs/rtrs-clt.c:1687 rtrs_clt_rdma_cm_handler+0x620/0x640 [rtrs_client]
>>       Modules linked in: rnbd_client rtrs_client rtrs_core rdma_cm iw_cm ib_cm rdma_rxe ib_uverbs ib_core libiscsi scsi_transport_iscsi crc32_generic udp_tunnel dax_pmem nd_pmem nd_btt virtiofs crc32c_intel nvme fuse nvme_core nfit
>> libnvdimm dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_mirror dm_region_hash dm_log dm_mod [last unloaded: ib_core]
>>       CPU: 0 PID: 14766 Comm: kworker/u2:3 Kdump: loaded Tainted: G        W          6.2.0-rc6-roce-flush+ #56
>>       Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
>>       Workqueue: ib_addr process_one_req [ib_core]
>>       RIP: 0010:rtrs_clt_rdma_cm_handler+0x620/0x640 [rtrs_client]
>>       Code: 00 0f 85 5f fd ff ff 4c 8b 23 41 bd f4 ff ff ff e9 95 fb ff ff 0f 0b 4c 89 f7 41 bd ea ff ff ff e8 75 c8 92 ec e9 4b ff ff ff <0f> 0b 4c 89 f7 41 bd ea ff ff ff e8 60 c8 92 ec e9 36 ff ff ff e8
>>       RSP: 0018:ffffa4ef41cdbc60 EFLAGS: 00010246
>>       RAX: 0000000000000000 RBX: ffff9372c394e600 RCX: 0000000000000001
>>       RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffad634277
>>       RBP: ffffa4ef41cdbd00 R08: 0000000000000000 R09: 0000000000000001
>>       R10: 0000000000003ff3 R11: 0000000000000000 R12: ffff9372c3164800
>>       R13: ffff9372c3164800 R14: ffff9372c394e640 R15: ffff9372c5219020
>>       FS:  0000000000000000(0000) GS:ffff9372fbc00000(0000) knlGS:0000000000000000
>>       CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>       CR2: 00007f35bb7d5de0 CR3: 0000000020c2a006 CR4: 00000000001706f0
>>       DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>       DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>       Call Trace:
>>        <TASK>
>>        ? mark_held_locks+0x49/0x80
>>        ? lock_is_held_type+0xd7/0x130
>>        ? cma_cm_event_handler+0x49/0x200 [rdma_cm]
>>        cma_cm_event_handler+0x49/0x200 [rdma_cm]
>>        addr_handler+0xf1/0x1e0 [rdma_cm]
>>        ? lock_acquire+0xca/0x2f0
>>        ? lock_acquire+0xda/0x2f0
>>        process_one_req+0x43/0x170 [ib_core]
>>        process_one_work+0x274/0x590
>>        worker_thread+0x4f/0x3d0
>>        ? __pfx_worker_thread+0x10/0x10
>>        kthread+0xe7/0x110
>>        ? __pfx_kthread+0x10/0x10
>>        ret_from_fork+0x2c/0x50
>>        </TASK>
>>       irq event stamp: 1432669
>>       hardirqs last  enabled at (1432683): [<ffffffffac508eb2>] __up_console_sem+0x52/0x60
>>       hardirqs last disabled at (1432698): [<ffffffffac508e97>] __up_console_sem+0x37/0x60
>>       softirqs last  enabled at (1432518): [<ffffffffac48c985>] __irq_exit_rcu+0xc5/0x120
>>       softirqs last disabled at (1432509): [<ffffffffac48c985>] __irq_exit_rcu+0xc5/0x120
>>       ---[ end trace 0000000000000000 ]---
>>
>> Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
>> ---
>>   drivers/infiniband/ulp/rtrs/rtrs-clt.c | 14 ++++++++++----
>>   1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>> index 4c8f42e46e2f..760a7eb51297 100644
>> --- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>> +++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>> @@ -2074,6 +2074,7 @@ static int create_cm(struct rtrs_clt_con *con)
>>           rtrs_err(s, "Failed to resolve address, err: %d\n", err);
>>           goto destroy_cm;
>>       }
>> +again:
>>       /*
>>        * Combine connection status and session events. This is needed
>>        * for waiting two possible cases: cm_err has something meaningful
>> @@ -2083,10 +2084,15 @@ static int create_cm(struct rtrs_clt_con *con)
>>               clt_path->state_wq,
>>               con->cm_err || clt_path->state != RTRS_CLT_CONNECTING,
>>               msecs_to_jiffies(RTRS_CONNECT_TIMEOUT_MS));
>> -    if (err == 0 || err == -ERESTARTSYS) {
>> -        if (err == 0)
>> -            err = -ETIMEDOUT;
>> -        /* Timedout or interrupted */
>> +    if (err == -ERESTARTSYS) {
>> +        /* interrupted,
>> +         * try again to avoid the in-flight rtrs_clt_rdma_cm_handler()
>> +         * getting a use-after-free
>> +         */
>> +        goto again;
>> +    } else if (err == 0) {
>> +        err = -ETIMEDOUT;
>> +        /* Timedout */
>>           goto errr;
>>       }
> 
> Can event handler still be triggered in case of timeout?

I have never hit such race.

> 
> And I guess either stop_cm -> rdma_disconnect or destroy_cm -> rdma_destroy_id
> should prevent this kind of racy issue.

In practice, they are possible that rtrs_clt_rdma_cm_handler() is in-flight during
'either stop_cm -> rdma_disconnect or destroy_cm -> rdma_destroy_id'. rtrs_clt_rdma_cm_handler() and
cm's cleanup path need to hold mutex_lock(&con->con_mutex), once cm's cleanup path get this lock first
rtrs_clt_rdma_cm_handler has to sleep, when rtrs_clt_rdma_cm_handler is wakeup again, some resources has been
freed by cm's cleanup path.

Thanks

> 
> Thanks,
> Guoqing