linux-ext4 - Re: [PATCH] debugfs: fix memory leak problem in read

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Date:   Fri, 26 Feb 2021 09:18:53 +0800
From:   Zhiqiang Liu <liuzhiqiang26@...wei.com>
To:     Theodore Ts'o <tytso@....edu>,
        harshad shirwadkar <harshadshirwadkar@...il.com>
CC:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        linfeilong <linfeilong@...wei.com>,
        lihaotian <lihaotian9@...wei.com>,
        "lijinlin (A)" <lijinlin3@...wei.com>
Subject: Re: [PATCH] debugfs: fix memory leak problem in read_list()

Thank you and harshad shirwadkar.

On 2021/2/26 1:02, Theodore Ts'o wrote:
> On Thu, Feb 25, 2021 at 07:51:09AM -0800, harshad shirwadkar wrote:
>> On Sat, Feb 20, 2021 at 12:41 AM Zhiqiang Liu <liuzhiqiang26@...wei.com> wrote:
>>>
>>>
>>> In read_list func, if strtoull() fails in while loop,
>>> we will return the error code directly. Then, memory of
>>> variable lst will be leaked without setting to *list.
>>>
>>> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@...wei.com>
>>> Signed-off-by: linfeilong <linfeilong@...wei.com>
>>> ---
>>>  debugfs/util.c | 12 ++++++++----
>>>  1 file changed, 8 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/debugfs/util.c b/debugfs/util.c
>>> index be6b550e..9e880548 100644
>>> --- a/debugfs/util.c
>>> +++ b/debugfs/util.c
>>> @@ -530,12 +530,16 @@ errcode_t read_list(char *str, blk64_t **list, size_t *len)
>>>
>>>                 errno = 0;
>>>                 y = x = strtoull(tok, &e, 0);
>>> -               if (errno)
>>> -                       return errno;
>>> +               if (errno) {
>>> +                       retval = errno;
>>> +                       break;
>>> +               }
>> Shouldn't we have `goto err;` here instead of break? strtoull failure
>> here indicates that no valid value was found, so instead of returning
>> the allocated memory, we should just free the memory and return error.
> 
> As of commit 462c424500a5 ("debugfs: fix memory allocation failures
> when parsing journal_write arguments") there is no longer the err:
> goto target.  The goal is to move to a model where the caller is
> exclusively responsible for freeing any allocated memory, since if
> realloc() has gotten into the act, the memory pointed to in *list
> would have been freed by realloc().  The fix is to make sure *list is
> updated before we return.  This also allows the caller to have access
> to the list of numbers parsed before we ran into an error.
> 
> So the Zhiqiang's patch is correc, and I will apply it.
> 
>        		  	   	       	 - Ted
> 
> .
>