Re: [PATCH v2] ksmbd: prevent memory leak on error return

[Namjae Jeon]

2023-11-19 18:14 GMT+09:00, Pierre Mariani <pierre.mariani@xxxxxxxxx>:
> On 11/8/2023 5:17 PM, Zongmin Zhou wrote:
>> When allocated memory for 'new' failed,just return
>> will cause memory leak of 'ar'.
>>
>> v2: rollback iov_alloc_cnt when allocate memory failed.
>>
>> Fixes: 1819a9042999 ("ksmbd: reorganize ksmbd_iov_pin_rsp()")
>>
>> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>> Reported-by: Dan Carpenter <error27@xxxxxxxxx>
>> Closes: https://lore.kernel.org/r/202311031837.H3yo7JVl-lkp@xxxxxxxxx/
>> Signed-off-by: Zongmin Zhou<zhouzongmin@xxxxxxxxxx>
>> ---
>>  fs/smb/server/ksmbd_work.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/smb/server/ksmbd_work.c b/fs/smb/server/ksmbd_work.c
>> index a2ed441e837a..44bce4c56daf 100644
>> --- a/fs/smb/server/ksmbd_work.c
>> +++ b/fs/smb/server/ksmbd_work.c
>> @@ -123,8 +123,11 @@ static int __ksmbd_iov_pin_rsp(struct ksmbd_work
>> *work, void *ib, int len,
>>  		new = krealloc(work->iov,
>>  			       sizeof(struct kvec) * work->iov_alloc_cnt,
>>  			       GFP_KERNEL | __GFP_ZERO);
>> -		if (!new)
>> +		if (!new) {
>> +			kfree(ar);
>> +			work->iov_alloc_cnt -= 4;
>>  			return -ENOMEM;
>> +		}
>>  		work->iov = new;
>>  	}
>>
>
> A few lines above, ar is allocated inside the 'if (aux_size)' block.
> If aux_size is falsy, isn't it possible that ar will be NULL hence
> we should have 'if (ar) kfree(ar);'?
We need to initialize ar to NULL on that case. And Passing a NULL
pointer to kfree is safe, So NULL check before kfree() is not needed.

Thanks.
>