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

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Message-ID: <CAKYAXd-2vR7KF=gwKWmA+a3XkAOG78ntPq__u4P5Kqo35N1D5Q@mail.gmail.com>
Date:   Sun, 19 Nov 2023 23:17:24 +0900
From:   Namjae Jeon <linkinjeon@...nel.org>
To:     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>,
        Zongmin Zhou <zhouzongmin@...inos.cn>
Subject: Re: [PATCH v2] ksmbd: prevent memory leak on error return

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.

Thanks.
>