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

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Message-ID: <313c7290-1f8c-4944-a420-be23d28e59fa@kylinos.cn>
Date:   Mon, 20 Nov 2023 09:33:35 +0800
From:   Zongmin Zhou <zhouzongmin@...inos.cn>
To:     Namjae Jeon <linkinjeon@...nel.org>,
        Pierre Mariani <pierre.mariani@...il.com>
Cc:     Zongmin Zhou <min_halo@....com>, linux-cifs@...r.kernel.org,
        linux-kernel@...r.kernel.org, senozhatsky@...omium.org,
        sfrench@...ba.org, tom@...pey.com,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <error27@...il.com>
Subject: Re: [PATCH v2] ksmbd: prevent memory leak on error return


On 2023/11/19 22:17, Namjae Jeon wrote:
> 2023-11-19 18:14 GMT+09:00, Pierre Mariani <pierre.mariani@...il.com>:
>> 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@...el.com>
>>> Reported-by: Dan Carpenter <error27@...il.com>
>>> Closes: https://lore.kernel.org/r/202311031837.H3yo7JVl-lkp@intel.com/
>>> Signed-off-by: Zongmin Zhou<zhouzongmin@...inos.cn>
>>> ---
>>>   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.
Yes, ar should be initialized to NULL to avoid the case of  aux_size 
will be false.
Since kfree(NULL) is safe.
Should I  send another patch for this?

Best regards!
> Thanks.