linux-kernel - Re: [PATCH] RDMA/restrack: Fix potential invalid address access

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Date: Mon, 4 Mar 2024 11:21:19 +0800
From: Wenchao Hao <haowenchao2@...wei.com>
To: Leon Romanovsky <leon@...nel.org>
CC: Jason Gunthorpe <jgg@...pe.ca>, <linux-rdma@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RDMA/restrack: Fix potential invalid address access

On 2024/3/3 20:57, Leon Romanovsky wrote:
> On Fri, Mar 01, 2024 at 05:55:15PM +0800, Wenchao Hao wrote:
>> struct rdma_restrack_entry's kern_name was set to KBUILD_MODNAME
>> in ib_create_cq(), while if the module exited but forgot del this
>> rdma_restrack_entry, it would cause a invalid address access in
>> rdma_restrack_clean() when print the owner of this rdma_restrack_entry.
> 
> How is it possible to exit owner module without cleaning the resources?
> 

I meet this issue with one of our product who develop their owner kernel
modules based on ib_core, and there are terrible logic with the exit
code which cause resource leak.

Of curse it's bug of module who did not clear resource when exit, but
I think ib_core should avoid accessing memory of other modules directly
to provides better stability.

What's more, from the context of rdma_restrack_clean() when print
"restack: %s %s object allocated by %s is not freed ...", it seems
designed for the above scene where client has bug to alerts there
are resource leak, so we should not panic on this log print.

> Thanks
> 
>>
>> Fix this issue by using kstrdup() to set rdma_restrack_entry's
>> kern_name.
>>
>> Signed-off-by: Wenchao Hao <haowenchao2@...wei.com>
>> ---
>>   drivers/infiniband/core/restrack.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/infiniband/core/restrack.c b/drivers/infiniband/core/restrack.c
>> index 01a499a8b88d..6605011c4edc 100644
>> --- a/drivers/infiniband/core/restrack.c
>> +++ b/drivers/infiniband/core/restrack.c
>> @@ -177,7 +177,8 @@ static void rdma_restrack_attach_task(struct rdma_restrack_entry *res,
>>   void rdma_restrack_set_name(struct rdma_restrack_entry *res, const char *caller)
>>   {
>>   	if (caller) {
>> -		res->kern_name = caller;
>> +		kfree(res->kern_name);
>> +		res->kern_name = kstrdup(caller, GFP_KERNEL);
>>   		return;
>>   	}
>>   
>> @@ -195,7 +196,7 @@ void rdma_restrack_parent_name(struct rdma_restrack_entry *dst,
>>   			       const struct rdma_restrack_entry *parent)
>>   {
>>   	if (rdma_is_kernel_res(parent))
>> -		dst->kern_name = parent->kern_name;
>> +		dst->kern_name = kstrdup(parent->kern_name, GFP_KERNEL);
>>   	else
>>   		rdma_restrack_attach_task(dst, parent->task);
>>   }
>> @@ -306,6 +307,7 @@ static void restrack_release(struct kref *kref)
>>   		put_task_struct(res->task);
>>   		res->task = NULL;
>>   	}
>> +	kfree(res->kern_name);
>>   	complete(&res->comp);
>>   }
>>   
>> -- 
>> 2.32.0
>>