Re: [PATCH for-next v2] RDMA/rxe: Fix mr->map double free

["lizhijian@fujitsu.com" <lizhijian@fujitsu.com>]

On 16/11/2022 08:10, Yanjun Zhu wrote:
>>
>> index d4f10c2d1aa7..7c99d1591580 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_mr.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
>> @@ -99,6 +99,7 @@ static int rxe_mr_alloc(struct rxe_mr *mr, int num_buf)
>>           kfree(mr->map[i]);
>>       kfree(mr->map);
>> +    mr->map = NULL;
>>   err1:
>>       return -ENOMEM;
>>   }
>> @@ -122,7 +123,6 @@ int rxe_mr_init_user(struct rxe_dev *rxe, u64 
>> start, u64 length, u64 iova,
>>       int            num_buf;
>>       void            *vaddr;
>>       int err;
>> -    int i;
>>       umem = ib_umem_get(&rxe->ib_dev, start, length, access);
>>       if (IS_ERR(umem)) {
>> @@ -163,9 +163,8 @@ int rxe_mr_init_user(struct rxe_dev *rxe, u64 
>> start, u64 length, u64 iova,
>>                   pr_warn("%s: Unable to get virtual address\n",
>>                           __func__);
>>                   err = -ENOMEM;
>> -                goto err_cleanup_map;
>> +                goto err_release_umem;
> 
> This call trace results from page_address's returning NULL, then goto 
> err_cleanup_map where mr->map[i] and mr->map are freed.
> 
> And finally rxe_reg_user_mr gets an error from rxe_mr_init_user, the 
> function rxe_mr_cleanup is called to handle mr to free mr->map[i] and 
> mr->map again.
> 
> So mr->map[i] and mr->map are double freed.
> 
> As such, this commit is reasonable.
> 
> But why page_address will return NULL?

ENOMEM? but I don't think we need taking too much care upon the reason.

this patch is most likely porting the reverted back, commit: 
8ff5f5d9d8cf ("RDMA/rxe: Prevent double freeing rxe_map_set()")

Actually, the double free can be triggered by below error path too.

149         err = rxe_mr_alloc(mr, num_buf); 

150         if (err) { 

151                 pr_warn("%s: Unable to allocate memory for map\n", 

152                                 __func__); 

153                 goto err_release_umem; 

154         }

where rxe_mr_alloc() freed the memory but don't set 'mr->map = NULL'

Thanks
Zhijian


> 
> Zhu Yanjun
>