Subject: Re: [PATCH] svcrdma: fix miss destroy percpu_counter in svc_rdma_proc_init()

From: yebin <[email-masked]>
Date: Mon, 4 Nov 2024 22:08:56 +0800

On 2024/11/2 0:27, Chuck Lever wrote:
> On Fri, Nov 01, 2024 at 11:55:11AM +0000, Simon Horman wrote:
>> On Thu, Oct 24, 2024 at 09:55:20AM +0800, Ye Bin wrote:
>>> From: Ye Bin <[email-masked]>
>>>
>>> There's issue as follows:
>>> RPC: Registered rdma transport module.
>>> RPC: Registered rdma backchannel transport module.
>>> RPC: Unregistered rdma transport module.
>>> RPC: Unregistered rdma backchannel transport module.
>>> BUG: unable to handle page fault for address: fffffbfff80c609a
>>> PGD 123fee067 P4D 123fee067 PUD 123fea067 PMD 10c624067 PTE 0
>>> Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI
>>> RIP: 0010:percpu_counter_destroy_many+0xf7/0x2a0
>>> Call Trace:
>>>   <TASK>
>>>   __die+0x1f/0x70
>>>   page_fault_oops+0x2cd/0x860
>>>   spurious_kernel_fault+0x36/0x450
>>>   do_kern_addr_fault+0xca/0x100
>>>   exc_page_fault+0x128/0x150
>>>   asm_exc_page_fault+0x26/0x30
>>>   percpu_counter_destroy_many+0xf7/0x2a0
>>>   mmdrop+0x209/0x350
>>>   finish_task_switch.isra.0+0x481/0x840
>>>   schedule_tail+0xe/0xd0
>>>   ret_from_fork+0x23/0x80
>>>   ret_from_fork_asm+0x1a/0x30
>>>   </TASK>
>>>
>>> If register_sysctl() return NULL, then svc_rdma_proc_cleanup() will not
>>> destroy the percpu counters which init in svc_rdma_proc_init().
>>> If CONFIG_HOTPLUG_CPU is enabled, residual nodes may be in the
>>> 'percpu_counters' list. The above issue may occur once the module is
>>> removed. If the CONFIG_HOTPLUG_CPU configuration is not enabled, memory
>>> leakage occurs.
>>> To solve above issue just destroy all percpu counters when
>>> register_sysctl() return NULL.
>>>
>>> Fixes: 1e7e55731628 ("svcrdma: Restore read and write stats")
>>> Fixes: 22df5a22462e ("svcrdma: Convert rdma_stat_sq_starve to a per-CPU counter")
>>> Fixes: df971cd853c0 ("svcrdma: Convert rdma_stat_recv to a per-CPU counter")
>>> Signed-off-by: Ye Bin <[email-masked]>
>>> ---
>>>   net/sunrpc/xprtrdma/svc_rdma.c | 18 +++++++++++++-----
>>>   1 file changed, 13 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/net/sunrpc/xprtrdma/svc_rdma.c b/net/sunrpc/xprtrdma/svc_rdma.c
>>> index 58ae6ec4f25b..11dff4d58195 100644
>>> --- a/net/sunrpc/xprtrdma/svc_rdma.c
>>> +++ b/net/sunrpc/xprtrdma/svc_rdma.c
>>> @@ -233,25 +233,33 @@ static int svc_rdma_proc_init(void)
>>>   
>>>   	rc = percpu_counter_init(&svcrdma_stat_read, 0, GFP_KERNEL);
>>>   	if (rc)
>>> -		goto out_err;
>>> +		goto err;
>>>   	rc = percpu_counter_init(&svcrdma_stat_recv, 0, GFP_KERNEL);
>>>   	if (rc)
>>> -		goto out_err;
>>> +		goto err_read;
>>>   	rc = percpu_counter_init(&svcrdma_stat_sq_starve, 0, GFP_KERNEL);
>>>   	if (rc)
>>> -		goto out_err;
>>> +		goto err_recv;
>>>   	rc = percpu_counter_init(&svcrdma_stat_write, 0, GFP_KERNEL);
>>>   	if (rc)
>>> -		goto out_err;
>>> +		goto err_sq;
>>>   
>>>   	svcrdma_table_header = register_sysctl("sunrpc/svc_rdma",
>>>   					       svcrdma_parm_table);
>>> +	if (!svcrdma_table_header)
>> Hi Ye Bin,
>>
>> Should rc be set to a negative error value here,
>> as is the case for other error cases above?
>>
>> Flagged by Smatch.
> I can add "rc = -ENOMEM;" to the applied patch.
>
I'm sorry for the late reply. Thank you very much for your revision.
>>> +		goto err_write;
>>> +
>>>   	return 0;
>>>   
>>> -out_err:
>>> +err_write:
>>> +	percpu_counter_destroy(&svcrdma_stat_write);
>>> +err_sq:
>>>   	percpu_counter_destroy(&svcrdma_stat_sq_starve);
>>> +err_recv:
>>>   	percpu_counter_destroy(&svcrdma_stat_recv);
>>> +err_read:
>>>   	percpu_counter_destroy(&svcrdma_stat_read);
>>> +err:
>>>   	return rc;
>>>   }
>>>   
>>> -- 
>>> 2.34.1
>>>